34. | Principles of Surgery, Companion Handbook

Chapter 33 Abdominal Wall, Omentum, Mesentery, and Retroperitoneum

Principles of Surgery Companion Handbook

CHAPTER

33
ABDOMINAL WALL, OMENTUM, MESENTERY, AND RETROPERITONEUM

Anterior Abdominal Wall
	Rectus Sheath Hematoma
	Desmoid Tumor
Omentum
	Torsion
	Idiopathic Segmental Infarction
	Cysts
	Solid Tumors
Mesentery
	Mesenteric Circulatory Disease
	Aneurysms of the Splanchnic Arteries
	Nonspecific Mesenteric Lymphadenitis
	Mesenteric Panniculitis
	Tumors of the Mesentery
Retroperitoneum
	Idiopathic Retroperitoneal Fibrosis
	Retroperitoneal Tumors

ANTERIOR ABDOMINAL WALL

Rectus Sheath Hematoma

Bleeding into the rectus sheath produces a surgical picture that may simulate the acute surgical abdomen. Bleeding is usually the result of rupture of the epigastric artery or veins and may follow direct trauma or occur spontaneously in patients with debilitating diseases or blood dyscrasia and in patients on anticoagulation therapy. Bleeding also occurs without obvious trauma or disease after minor straining.

Clinical Manifestations Rectus sheath hematoma is three times more frequent in women; it is rare in children. The peak age of incidence is the fifth decade. The sudden onset of pain is localized to the side of the abdomen where the bleeding occurred. Anorexia, nausea, low-grade fever, and a moderate leukocytosis are frequent. A tender mass may be palpable. Ultrasonography or computed tomography (CT) shows complex lesions within the rectus sheath.

Treatment Rectus sheath hematoma may be managed nonoperatively with bed rest and analgesics. Surgical intervention is necessary occasionally; ideally, the hematoma is evacuated without entering the peritoneal cavity. Bleeding points are then ligated and the wound closed without drainage.

Desmoid Tumor

This is an aggressive variant within a group of conditions referred to as fibromatoses. Desmoid tumor is of aponeurotic origin and usually is found within or deep to the flat muscles of the anterior abdominal wall. It is often seen in women of childbearing age, frequently after a recent gestation, and it may be the result of hemorrhage. It also frequently occurs in patients with familial polyposis coli (Gardner syndrome) trait. Desmoid tumors are locally invasive benign tumors that rarely undergo malignant transformation to a low-grade fibrosarcoma; metastases have not been reported, but there is a tendency to recur after local excision. The microscopic appearance varies from an acellular fibroma to that of a cellular, low-grade fibrosarcoma.

Clinical Manifestations Desmoid tumor is usually a painless, deeply situated mass that is solitary, rarely crosses the midline, and may be fixed. It may vary in size from a few centimeters to a tumor weighing several kilograms. Desmoid tumors have a pseudocapsule with extensions into surrounding tissue, a feature critical to surgical management. The tumor locally invades and, although usually painless, can cause symptoms by compression of adjacent tissues such as nerves, bone, and viscera. Abdominal CT scan will show a homogeneous soft tissue mass with displacement of adjacent structures.

Treatment Once the diagnosis is established by biopsy, ideal treatment is wide excision with at least a 1–2-cm margin of normal tissue. This will include skin, muscle, and peritoneum. Every effort should be made to excise the tumor completely at the first operation, since there is a high propensity for local recurrence following incomplete excision.

In patients who are unresectable or with gross disease left at the margins, radiation therapy is recommended, although the reported response has been variable. Pharmacologic treatments also have been unpredictable, with most favorable reports anecdotal.

Recurrences can be treated by reexcision. For abdominal wall desmoids, prognosis is excellent. Prognosis for extraabdominal desmoids is less favorable.

OMENTUM

Torsion

Torsion is a twist on the long axis of the omentum to an extent causing vascular compromise. Primary omental torsion is relatively rare. Secondary omental torsion is associated with adhesions of the free end of the omentum to tumors, foci of intraabdominal inflammation, postoperative wounds, or internal or external hernias. Secondary torsion is more common than primary.

Clinical Manifestations Pain begins suddenly and is usually localized to the right lower quadrant. Tenderness, rebound tenderness, and voluntary spasm are frequent. The finding of free serosanguineous fluid at the time of celiotomy in the absence of a pathologic condition in the appendix, gallbladder, or pelvic organs should alert the surgeon to the possibility of omental torsion.

Treatment Treatment involves resection of the involved omentum with correction of any underlying etiologic condition.

Idiopathic Segmental Infarction

This is an acute vascular disturbance of the omentum not accompanied by omental torsion or an intraabdominal pathologic condition. It is precipitated by thrombosis of omental veins secondary to endothelial injury. The right lower segment of the omentum, which is the most mobile and richest in fat, is the portion usually involved. The involved segment is well demarcated, and serosanguineous fluid in the free peritoneal cavity is a constant finding.

Clinical Manifestations and Treatment Most patients are young or middle-aged adults who present with right-sided abdominal pain. There is always tenderness and often rebound tenderness over the region of the infarction. Resection of the infarcted area is indicated to prevent the possible complications of gangrene and adhesions.

Cysts

True omental cysts have an endothelial lining similar to cystic lymphangiomas. Dermoid cysts are lined with squamous epithelium and may contain hair, teeth, and sebaceous material. Pseudocysts of the omentum probably result from trauma with hematoma formation.

Clinical Manifestations Large cysts present as a palpable abdominal mass or with manifestations of torsion, infection, rupture, or intestinal obstruction.

Plain radiographs sometimes show a circumscribed soft tissue haziness. Ultrasound or CT shows a fluid-filled mass that often contains internal septations. Treatment consists of local excision.

Solid Tumors

The most common solid tumor of the omentum is metastatic carcinoma, which generally involves the omentum by tumor implant. Frequently there is associated ascites. Primary solid tumors of the omentum are rare. Most are tumors of smooth muscle, and about one-third are malignant. Excision is indicated.

MESENTERY

Mesenteric Circulatory Disease

ACUTE OCCLUSION OF THE SUPERIOR MESENTERIC ARTERY

This is due more often to an embolus than to thrombosis. Most emboli come from the heart and more often lodge near a major branch where the artery narrows, usually at the egress of the middle colic artery. The initial effect of the embolus on the artery is to cause spasm of its distal branches; secondary thrombosis of the distal artery then occurs. Sudden occlusion of the main stem superior mesenteric artery produces ischemia of the entire small intestine distal to the ligament of Treitz and also ischemia of the proximal half of the colon. Acute thrombosis of the superior mesenteric artery usually occurs in an artery partially occluded by atherosclerosis. The extent of intestinal ischemia or infarction depends on the site of the thrombosis and the status of collateral channels.

Pathology Early the bowel is pale due to intense vasospasm. At this stage, the bowel is hypertonic and contracted. Within 1–2 h, the initial vessel spasm subsides, and anoxic bowel wall becomes engorged with blood. Thrombosis of the visceral veins follows, and the bowel wall becomes inert, boggy, and cyanotic. As the infarction progresses to full-thickness necrosis of the intestine, the bowel wall becomes blood-soaked and cyanotic and “weeps” serosanguineous fluid into the peritoneal cavity.

Clinical Manifestations The clinical features are usually the same whether occlusion is the result of embolism or thrombosis. Males are affected more often than females. The peak age of incidence is the fifth and sixth decades. The most striking and constant complaint is sudden extreme abdominal pain initially out of proportion to the physical findings. Muscle spasm may be present, but the rigidity is almost never boardlike. Tenderness and rebound tenderness become severe as intestinal infarction occurs. Bowel sounds are first hyperactive, but within a short time the abdomen becomes silent. As infarction of the intestine progresses, the patient becomes febrile, the pulse rate increases, and the patient becomes hypotensive. Once bowel necrosis and perforation occur, the findings are those of generalized peritonitis and sepsis. The leukocyte count increases to over 20,000/mm³ as hemorrhagic infarction occurs. Suspicion of the diagnosis of acute mesenteric ischemia is itself an indication to obtain an immediate mesenteric arteriogram. In addition to demonstrating emboli, thrombosis, and mesenteric vasoconstriction, the arteriogram will define the adequacy of the splanchnic circulation. The angiographic catheter also provides a route for the intraarterial administration of vasodilating agents.

Treatment An occasional patient can be treated successfully by arterial infusion of a vasodilating agent. Early surgical intervention before gangrene and perforation of the intestine have occurred is optimal. The number of patients who present with a situation amenable to arterial reconstruction is small. If the occlusion is limited to a branch of the superior mesenteric artery or to the superior mesenteric artery distal to the origin of the ileocolic artery, the relatively short segments of affected intestine are best handled by resection with a primary anastomosis. As much as 70 percent of the small intestine can be removed without creating serious digestive disturbances.

In the situation where the main stem superior mesenteric artery is occluded, the decision to establish arterial flow is based on whether the process in the ischemic intestine is reversible. If the intestines are clearly gangrenous, the only surgical procedure that can be considered is resection. This usually will require removal of the entire small intestine distal to the ligament of Treitz and resection of the right half of the colon. Although this extensive resection is associated with a high operative mortality and late morbidity, it is worth consideration in an otherwise hopeless situation, and with the use of parenteral central hyperalimentation postoperatively, some patients can be salvaged.

If there is any question of the reversibility of ischemia of all or part of the intestine, an attempt at arterial reconstruction is indicated. An embolus usually can be extracted using a Fogarty catheter; a thrombus within a sclerotic vessel will require a thromboendarterectomy. An alternative approach is revascularization with a bypass venous graft between the aorta and the superior mesenteric artery distal to the site of occlusion.

Clinical assessment, such as return of intestinal color and arterial pulsations and the presence of visible peristalsis, is usually reliable in determining that a segment of revascularized intestine will remain viable. Intraoperative use of the Doppler ultrasonic flowmeter to detect pulsatile mural blood flow can give added objective confirmation. Intravenous infusion of a vital dye, usually fluorescein, also has been advocated to define intestinal recovery. If there is any question about the viability of long segments of intestine, they should be left and reexamined at a planned second operation 24–36 h later.

Most patients will have a depleted circulating blood volume resulting from loss of plasma and whole blood into the bowel lumen, bowel wall, and peritoneal cavity. Replacement should be started while readying the patient for the operation. Added intravenous fluids are necessary postoperatively to combat the reactive hyperemia that occurs after revascularization of the intestine. Broad-spectrum antibiotics should be administered in large doses beginning preoperatively and continuing throughout the postoperative period. Anticoagulation, preferably with heparin, also has been recommended for patients who have arterial reconstruction.

The overall mortality after sudden occlusion of the superior mesenteric artery varies between 60 and 85 percent. Mortality is higher after acute occlusion by thrombosis than from embolization.

NONOCCLUSIVE MESENTERIC INFARCTION

In about 30 percent of patients with mesenteric infarction, careful examination will reveal no major arterial or venous occlusion. The infarction has been related to a sustained decrease in cardiac output, such as in prolonged circulatory collapse and hypoxic states that may accompany septicemia, acute myocardial infarction, and profound hypovolemia. Many patients presenting with nonocclusive mesenteric infarction have received digitalis, an agent that has been shown to induce mesenteric vasoconstriction.

Pathology The outer surface of the bowel is initially mottled, with segmental areas of cyanosis distributed throughout the length of the intestine. Later, gangrenous changes become advanced and lead to perforation.

Clinical Manifestations The clinical picture may be identical to that of patients with acute arterial or venous mesenteric occlusions. There may be prodromal symptoms of malaise and vague abdominal discomfort. Infarction of the intestine is heralded by the sudden onset of severe abdominal pain and vomiting. The patient usually becomes acutely hypotensive with a rapid pulse. Watery diarrhea is frequent, and the stools may be grossly bloody. The abdomen becomes diffusely tender and rigid. Bowel sounds are diminished or absent. Fever and leukocytosis are usual, and frequently there is a thrombocytopenia related to intravascular thrombosis. A characteristic early laboratory finding is a markedly elevated hematocrit due to “trapping” of serum in the bowel and seepage into the peritoneal cavity. Selective superior mesenteric arteriograms will demonstrate patent major vessels with multiple segmental areas of narrowing of both small and medium-sized vessels and diminution or absence of mural intestinal circulation.

Treatment The underlying disorder producing the low-flow state should be corrected. An attempt should be made to improve mesenteric artery flow. Direct infusion of a vasodilating drug, such as papaverine hydrochloride, into a catheter positioned in the superior mesenteric artery is used to improve mesenteric arterial flow. Antibiotics should be administered.

If abdominal signs and symptoms persist, operation is mandatory. The process usually involves all of both the large and small intestines and also may involve the stomach. For this reason, resection is not usually feasible. With involvement of lesser portions of the intestine, primary resection with anastomosis should be attempted. The reported mortality rates are upward of 80 percent.

CHRONIC OCCLUSION OF THE SUPERIOR MESENTERIC ARTERY (INTESTINAL ANGINA)

Intestinal ischemia, “intestinal angina,” without infarction is due to collateral blood supply sufficient for life but not for function of the affected bowel. This is analogous to angina pectoris and intermittent claudication.

Etiology Collateral anastomoses among the three main gastrointestinal arteries from the aorta (celiac axis, superior mesenteric, and inferior mesenteric) provide for maintenance of intestinal viability and function when one of these branches is gradually occluded. When one main vessel is occluded and blood flow through one of the remaining patent vessels becomes (or has been) compromised, the now relatively ischemic intestine is unable to respond to the demands of digestion for an increased blood supply.

Chronic occlusion of the major visceral arteries is most often due to atherosclerosis. Less frequently, the stenosis is due to compression of the celiac axis by a celiac ganglion or arcuate ligament of the diaphragm, by involvement of the arteries in an expanding aortic aneurysm, or by an arteritis.

Clinical Manifestations The dominant feature of intestinal angina is generalized cramping abdominal pain that comes on soon after eating. The food-pain relationship soon leads to a reluctance on the part of the patient to eat. Subsequent rapid and severe weight loss characterizes the syndrome. As the intestinal ischemia progresses, a form of malabsorption syndrome contributes to the weight loss. An arteriogram will show stenosis or complete occlusion of the celiac axis or superior mesenteric arteries or both, usually within 1 cm of their origin.

Treatment Most surgeons prefer improving the circulation with a bypass graft. For a lesion in the celiac artery, a graft is inserted between a major branch of the celiac artery, usually the splenic artery, and the aorta.

Occasionally, the splenic artery itself may be mobilized and anastomosed to the side of the aorta. Bypassing of a superior mesenteric artery stenosis is best handled by inserting a graft to the side of the artery just beyond the egress of the middle colic artery and to the aorta below the origin of the renal arteries.

COLONIC ISCHEMIA

Etiology This occurs in elderly patients with underlying atherosclerotic stenoses or inflammatory arteriopathies. It sometimes follows ligation of the inferior mesenteric artery during aortic aneurysmectomy in the setting of stenosis of the superior mesenteric artery. The ischemia most often involves the descending and sigmoid colon.

Clinical Manifestations The clinical manifestations are characterized by sudden cramping lower abdominal pain and the urge to defecate followed in 12–24 h by passage of melena or bloody stool.

Plain x-rays may show thumbprinting of the colon, indicative of submucosal edema. The primary diagnostic study is flexible sigmoidoscopy, which will visualize patchy areas of ischemia or, if advanced, frank mucosal necrosis.

Treatment The condition is reversible in 40–50 percent of patients requiring only supportive measures, with results ranging from complete healing to stricture formation. This occurs when the ischemia is limited to mucosa or submucosa. When frank transmural necrosis is seen on initial sigmoidoscopy (serially), or when symptoms and endoscopic findings are progressive, early operation is indicated. Because the bowel is rarely prepared, ideal treatment is resection of all ischemic colon with end-colostomy and mucous fistula or Hartman's procedure.

MESENTERIC VENOUS OCCLUSION

Etiology and Pathology When visceral venous occlusion produces symptoms, it is almost always due to acute thrombosis. Mesenteric venous thrombosis may be idiopathic or evolve secondarily as a complication of several clinical disorders. Predisposing conditions include (1) intraabdominal infection, (2) portal hypertension, (3) hematologic conditions such as polycythemia vera, myeloproliferative disorders, or postsplenectomy state, (4) oral contraceptive use, (5) malignancy, and (6) the postoperative state. Congenital absence of naturally occurring antithrombotic proteins such as protein S, protein C, and antithrombin III explains the pathogenesis of most cases previously thought to be idiopathic. About 50 percent of patients give a history of prior episodes of peripheral deep venous thrombosis.

Clinical Manifestation Frequently, the patient complains of vague abdominal discomfort, anorexia, and a change in bowel habits a few days or even weeks before the onset of severe symptoms. Early symptoms are followed by sudden severe abdominal pain, vomiting, and circulatory collapse. Bloody diarrhea is more frequent than with arterial occlusion. Rigidity is not present unless gangrene and perforation of the bowel have occurred. A marked leukocytosis and elevated hematocrit are characteristic findings in venous thrombosis. Paracentesis invariably yields serosanguineous fluid. Contrast-enhanced abdominal CT scan is the most useful diagnostic modality. This will show thickening of the bowel wall, possibly air in the bowel wall or portal vein, and often thrombus in the superior mesenteric vein.

Treatment Without operation, the mortality approaches 100 percent. Once diagnosed, heparin anticoagulation should be started immediately. Patients with peritoneal sign should undergo early operation soon after receiving supportive fluids and antibiotics. Shorter segments of intestine are usually involved than that noted if occlusion is primarily arterial. All devitalized intestine is resected, and a primary end-to-end anastomosis is performed. Resection should include adjacent normal bowel and mesentery until all grossly thrombosed veins are encompassed.

A “second look” operation 24–36 h later should be performed because of the frequent recurrence of thrombosis or extension of residual clots. Anticoagulation with heparin should be continued for 6–8 weeks. The prognosis is somewhat better than in mesenteric infarction due to arterial occlusion.

Aneurysms of the Splanchnic Arteries

Aneurysms of the splanchnic arteries are rare. Arteriosclerosis is the usual etiology in older patients; congenital or acquired defects in the medial wall of the artery are more often incriminated in the young.

Splenic artery aneurysms compromise about 60 percent. Most occur in women, and in about 40 percent of patients the aneurysms are multiple. Hepatic artery aneurysms make up 16–20 percent. Aneurysms of the celiac artery and the superior mesenteric artery and its branches each account for about 3 percent. Most are due to arteriosclerosis, but a relatively large number of aneurysms of the superior mesenteric artery result from mycotic involvement or necrotizing arteritis.

Most splanchnic artery aneurysms are less than 2 cm in diameter. About 2–10 percent of splenic artery aneurysms rupture; the risk of rupture of hepatic, celiac, and superior mesenteric artery aneurysms is high, approximating 50 percent.

Clinical Manifestations Before rupture, most splanchnic artery aneurysms are asymptomatic. Concentric calcification of a splenic artery aneurysm may be detected on plain x-rays of the abdomen. Occasionally, a visceral artery aneurysm will be diagnosed prior to rupture on an incidental arteriogram obtained for another purpose.

When rupture occurs, the major symptom is acute abdominal pain and signs of acute blood loss. A splenic artery aneurysm rarely will rupture into the adjacent stomach or pancreatic duct, causing massive gastrointestinal bleeding. Erosion of a hepatic artery aneurysm into the bile duct is an unusual cause of hemobilia, with the classic triad of gastrointestinal bleeding, biliary colic, and jaundice.

Treatment A conservative approach is justified for the asymptomatic patient with a small splenic artery aneurysm. There is a hazard of rupture during pregnancy, notably during the third trimester. Operation is indicated for women of childbearing age. The preferred treatment is proximal and distal ligation of the aneurysm with obliteration of all feeding vessels in order to avoid splenectomy. If this is not feasible, resection of the aneurysm and splenectomy will be necessary. Because risk of rupture of other splanchnic artery aneurysms is high, asymptomatic patients should undergo surgical correction as soon as the aneurysm is recognized. Percutaneous transcatheter embolization is useful for treatment of intrahepatic aneurysms and other aneurysms of noncritical vessels.

Patients presenting with a ruptured aneurysm and with either intraabdominal or intraintestinal blood loss require immediate resuscitation and surgical intervention. If time allows, preoperative localization by arteriography should be carried out. The chances of finding the bleeding site are better if the blood pressure can be elevated preoperatively, but sometimes bleeding is so brisk that it is necessary to go to the operating room while the patient is in shock.

Rupture of a celiac artery aneurysm can be treated by ligation, and although most hepatic artery aneurysms also can be treated safely by ligation, an attempt should be made to reconstruct the hepatic artery with a graft. Rupture of a main superior mesenteric artery aneurysm will require replacement with a graft, preferably of autogenous vein. Overall mortality following rupture of a splenic artery aneurysm is about 25 percent, with a 65 percent maternal and 95 percent fetal mortality if rupture occurs during pregnancy. The mortality subsequent to rupture of a celiac or superior mesenteric artery aneurysm is between 40 and 60 percent, whereas rupture of a hepatic aneurysm is associated with a 70 percent mortality rate.

Nonspecific Mesenteric Lymphadenitis

Nonspecific mesenteric lymphadenitis is one of the common causes of acute abdominal pain in young children. The lymph nodes primarily involved are those which drain the ileocecal region.

Clinical Manifestations The disease most commonly occurs in patients under age 18, without sex predilection. The initial pain is usually in the upper abdomen. Eventually the pain localizes to the right side; however, an important point in differentiating the disease from acute appendicitis is that the patient is unable to indicate the exact site of the most intense pain. The usual finding on examination of the abdomen is tenderness in the lower aspect of the right side, which is somewhat higher and more medial and considerably less severe than in acute appendicitis. The clinical similarity to acute appendicitis is marked.

Mesenteric Panniculitis

Mesenteric panniculitis is a process of extensive thickening of the mesentery by a nonspecific inflammatory process. Many consider it a variant of retroperitoneal fibrosis. The cause is unknown. Usually it involves the mesenteric root of the small bowel. Grossly, the normal fat lobulations of the markedly thickened and firm mesentery are lost. Scattered throughout are irregular areas of discoloration that vary from reddish-brown plaques to pale-yellow foci resembling fat necrosis.

Clinical Manifestations Men are affected more often than women. The disease is rarely described in children. The clinical features are nonspecific; they include recurrent episodes of moderate to severe abdominal pain, nausea, vomiting, and malaise. CT scan demonstrates mesenteric panniculitis as a localized fat-dense mass containing areas of increased density representing fibrosis.

Treatment Laparotomy is necessary to establish the diagnosis and to rule out other tumefactions of the abdomen. Widespread involvement of the mesentery precludes more than biopsy. Since neoplasms of the mesenteric lymph nodes may present a similar gross appearance, several biopsies from different sites should be obtained. The inflammatory process is self-limiting and seldom causes any serious complications.

Tumors of the Mesentery

Tumors originating between the leaves of the mesentery are quite rare. In contrast, malignant implants from intraabdominal or pelvic tumors or metastases to mesenteric lymph nodes are relatively common.

Pathology Primary tumors of the mesentery may be cystic or solid. A classification of these tumors is shown in Table 33-1. Most cystic mesenteric tumors are benign. Benign solid tumors of the mesentery are more common than malignant ones. Solid malignant tumors arise near the root of the mesentery; solid benign tumors have a greater tendency to develop peripherally near the intestine.

TABLE 33-1 CLASSIFICATION OF PRIMARY MESENTERIC TUMORS

Clinical Manifestations In most patients, symptoms are few or nonexistent, and the tumor is detected during routine examination. Only rarely will the patient present with symptoms of complete intestinal obstruction or symptoms resulting from complications of the tumor per se such as torsion, hemorrhage, or infarction of the tumor mass. In the absence of intestinal obstruction or these complications, the sole finding will be the presence of a nontender intraabdominal mass, usually in the lower right part of the abdomen. The mass varies in size from a few inches in diameter to one that may fill the entire abdomen. Extremely large masses are usually cystic, in which case they are tense and fluctuant. Both cystic and solid tumors of the mesentery are laterally mobile; they can be moved easily from side to side but only slightly in an upward and downward direction.

Imaging techniques are the most useful means for diagnosing both cystic and solid mesenteric tumors. On ultrasonography, a mesenteric cyst appears as a well-outlined sonolucent transonic abdominal mass. CT demonstrates a simple mesenteric cyst as a nonenhancing near-water-density mass with a thin wall and a solid tumor as a mass lesion with a soft tissue density.

Treatment Surgical excision is the only treatment for benign and malignant lesions. All mesenteric cysts of a size sufficient to be palpated should be removed if at all possible, since even benign lesions eventually cause pain and compression of neighboring structures. Benign cystic tumors can be removed by enucleation or local excision. Wide excision, together with resection of adjacent intestine, is recommended for benign solid tumors, since these have a tendency toward local recurrence and malignant degeneration. Few patients with malignant primary mesenteric tumors are alive after 5 years.

RETROPERITONEUM

Idiopathic Retroperitoneal Fibrosis

This is a nonspecific, nonsuppurative inflammation of fibroadipose tissue that produces symptoms by the gradual compression of the tubular structures in the retroperitoneal space. The disease represents one of the manifestations of a widespread entity termed systemic idiopathic fibrosis. Idiopathic mediastinal fibrosis, Riedel's struma, sclerosing cholangitis, panniculitis, Peyronie's disease, and desmoid tumor are other fibromatoses that are considered localized forms of a systemic idiopathic fibrosis.

The lesion consists of a plaque of woody, white fibrous tissue that is distributed along the course of the periaortic lymphatics. In about one-third of patients it is bilateral. The involved tissue surrounds and constricts but does not invade the regional structures in the retroperitoneum. The pattern varies from a subacute cellular process with polymorphonuclear cells, lymphocytes, fibroblasts, and fat cells to a completely hyalinized, relatively acellular sclerosis.

Clinical Manifestations Retroperitoneal fibrosis is two to three times more common among men than among women. Two-thirds of patients are 40–60 years old. The natural history of the disease has been divided into three periods: (1) the period of incidence and development, (2) the period of activity, i.e., spread of the cellular and fibrotic process to envelopment of the retroperitoneal structures, and (3) the period of contraction of the fibrotic mass with compression of the involved structures. The disease is apparently self-limiting once the fibrotic stage is reached, a factor of major importance in considering types of therapy. The first complaint is invariably dull, noncolicky pain. It usually originates in the flank or low back and often radiates to the lower abdomen, groin, genitalia, or anteromedial aspect of the thigh. The pain is unilateral at first but may become bilateral later, as the fibrotic process spreads. Moderate fever and leukocytosis are often present early; the erythrocyte sedimentation rate is elevated. A transabdominal or pelvic mass is palpable in about one-third of patients.

Symptoms due to compression of the tubular retroperitoneal structures may follow the initial complaints by 1 month to 2 years. The major structures involved are the ureters, aorta, and inferior vena cava. Partial or complete ureteral obstruction occurs in 75–85 percent of patients. As many as 40 percent of patients will have oliguria or anuria with laboratory evidence of uremia. Lower extremity edema occurs occasionally. Arterial insufficiency due to fibrous constriction of the aorta or iliac arteries is uncommon.

CT scan shows a homogeneous, soft tissue mass enveloping the ureters, aorta, and inferior vena cava. A triad that is highly suggestive of retroperitoneal fibrosis on the pyelogram is (1) hydronephrosis with a dilated, tortuous upper ureter, (2) medial deviation of the ureter, and (3) extrinsic ureteral compression.

Treatment Some patients improve with supportive measures. With the onset of urinary infection or depression of renal function, surgical intervention usually becomes necessary. Steroid-induced regression of the inflammatory edema may reestablish urinary patency and thus facilitate elective, rather than emergency, surgery.

Ureterolysis with intraperitoneal transplantation is currently the most effective means of relieving obstruction of the involved ureter. This consists of freeing the ureter from the enveloping mass of fibrous tissue and transferring it into the peritoneal cavity, closing the posterior peritoneum behind it. Aortic or iliac artery obstruction is best treated by arteriolysis or bypass with a synthetic vascular graft.

Symptoms due to venous obstruction are best treated with elevation and elastic support to the lower limbs until a sufficient collateral venous system develops. Release of the obstructed vein from its fibrous encasement may be difficult and hazardous, and bypass procedures for obstruction of the inferior vena cava have been uniformly unsuccessful. Prognosis of the disease is generally good if appropriate treatment begins before the development of irreversible renal damage.

Retroperitoneal Tumors

Lymphomas and retroperitoneal liposarcomas and leiomyosarcomas are the most common nonvisceral malignant tumors of the retroperitoneum. The majority occur in the fifth or sixth decade, with a peak incidence at about age 60. Approximately 15 percent are found in children under age 10. A classification of the benign and malignant tumors according to tissue type is given in Table 33-2.

TABLE 33-2 CLASSIFICATION OF RETROPERITONEAL TUMORS

The tumors may be solid, cystic, or a combination of both. Their color varies from white (fibroma), yellow (lipoma), or pinkish to red (sarcoma) depending on the predominant tissue. As a rule, the predominantly cystic tumors are benign; solid tumors are usually malignant.

Clinical Manifestations The tumor may attain large size before producing symptoms. As the tumor grows, it compresses, obstructs, or invades adjacent organs or structures so that the presenting symptoms are often referable to these organs. The initial manifestations include an enlarging abdomen, backache, a sense of fullness or heaviness, and vague, indefinite pain that later may become more severe and radicular. Pain radiating into one or both thighs is usually late and due to involvement of lumbar and sacral nerve routes; it invariably denotes a malignant tumor. The predominant physical finding is an abdominal mass.

The CT scan can demonstrate the contours of the tumor mass, its size and relationships, as well as its effects on adjacent viscera and other tissues. This information is useful in determining resectability of the tumor and in planning a surgical approach. Ultrasonography differentiates between solid and cystic tumors. Percutaneous needle biopsy directed by CT or ultrasonography can be used to obtain preoperative histologic diagnosis and for the detection of treatment failures and early recurrences.

Aortography should be a part of the workup of patients with a retroperitoneal tumor to define tumor size and can give useful information about the vascular anatomy.

Treatment Some retroperitoneal tumors are benign and can be cured by simple excision; some are histologically benign but clinically malignant; others grow slowly and tend to recur and invade locally; and still others are rapidly malignant from the start. Treatment of these growths consists of surgical or irradiation therapy or a combination of the two. With the exception of lymphomas, chemotherapy has only limited therapeutic application. Surgical treatment is most effective and offers the greatest prospect for cure. A cure may be anticipated following complete resection of a benign tumor. Because malignant tumors typically develop a pseudocapsule, local recurrence is frequent when they are simply enucleated. The tumors extend into the loose retroperitoneal tissue planes, and their frequent relationship to vital structures makes it difficult to obtain negative margins during tumor excision.

Metastases typically spread hematogenously. The most frequent site of metastases is to the liver and lung. Lymph node metastases are rare except for lymphomas.

Histologic grade is the most important factor in determining prognosis. As many as one-third of patients with malignant tumors may be inoperable because of distant metastases to liver, lungs, and bone, in order of frequency.

For a malignant tumor, the initial operation offers the best chance of cure. Fewer than 25 percent of malignant tumors can be resected completely with anticipation of cure.

Malignant retroperitoneal tumors have a high recurrence rate, 30–50 percent in most large series. The tumors become more malignant with each recurrence, and reoperation becomes more hazardous. Nevertheless, long-term survival has been reported after multiple resections. Five-year survival free of tumor is less than 10 percent.

For a more detailed discussion, see Daly JM, Adams JT, Fantini GA, and Fischer JE: Abdominal Wall, Omentum, Mesentery, and Retroperitoneum, chap. 33 in Principles of Surgery, 7th ed.