Small Bowel and Cecum

As the enzymes progress further down the root of the mesentery, jejunitis may be evident (Fig. 11-36). It has long been recognized that "sentinel loops" from localized paralytic ileus of small bowel may accompany pancreatitis.33 Jejunal and occasionally ileal changes characterized by marked persistent spasm of some segments and dilatation of others, with coarsening of the mucosal folds, may be seen (Figs. 11-37 and 11-38).

Ischemic changes in the intestine as well may be produced by the digestive effects of the liberated enzymes or by thrombosis from areas of fat necrosis. Microaneu-rysms, pseudoaneurysms, stenoses, and occlusions are being increasingly recognized in mesenteric vessels following pancreatitis.34,35 The vascular consequences may range from fibrotic strictures20,26 (Fig. 11-39) to gangrene of the bowel14,37-40 (Fig. 11-40).

Figure 11-41 illustrates the findings in a case of malabsorption and jejunal mucosal atrophy secondary to chronic relapsing pancreatitis. Protracted ischemia of the intestine from the vascular effects of pancreatic enzymes in the mesentery underlay the chronic malabsorption in this case. It thus appears that some of the features of pancreatic malabsorption may be on a vascular basis. Localized anatomic changes of mesenteric vessels from the digestive effects of pancreatic enzymes may result in vascular shunts and ischemic malabsorption.

Acute pancreatitis may clinically mimic an acute appendicitis with peritoneal signs localized predominantly in the right lower quadrant. This is a reflection of the process spreading along the length of the root of the small bowel mesentery to result in inflammatory changes of distal ileal loops or the cecum.2 Plain film findings text continues on page 590

Fig. 11—32. Spread of pancreatitis through the small bowel mesentery.

In a case of acute pancreatitis, CT shows the inflammatory reaction extending through the small bowel mesentery, displacing the superior mesenteric artery (a) and vein (v) and intestinal branches. The fat encircling the superior mesenteric artery is maintained. The process also extends within the extraperitoneal anterior pararenal space on the left. (Reproduced from Meyers et al.5)

Root Small Bowel Mesentery

Fig. 11—33. Opacification of mesenteric root in vivo.

(a and b) Injection of contrast material through tube draining a loculated pseudocyst (Ps) of the tail of the pancreas demonstrates communication dissecting along the root of the small bowel mesentery (arrows). Note its typically oblique course toward the right lower quadrant in relation to duodenum, jejunum, ileum, and cecum.

(Courtesy of Jack Farman, M.D., Columbia-Presbyterian Medical Center, New York, NY.)

Fig. 11—33. Opacification of mesenteric root in vivo.

(a and b) Injection of contrast material through tube draining a loculated pseudocyst (Ps) of the tail of the pancreas demonstrates communication dissecting along the root of the small bowel mesentery (arrows). Note its typically oblique course toward the right lower quadrant in relation to duodenum, jejunum, ileum, and cecum.

(Courtesy of Jack Farman, M.D., Columbia-Presbyterian Medical Center, New York, NY.)

Mesenteric Pseudocyst

Fig. 11—34. Spread of pancreatic pseudocyst down the mesenteric root.

(a) While a large pancreatic pseudocyst (PS,) occupies the lesser sac, a smaller one (PS2) has developed in the region of the uncinate process (U).

(b) The smaller pseudocyst has dissected down the root of the small bowel mesentery to reside in the right lower quadrant in relation to a distal ileal loop. (From Oliphant M, Berne AS.31)

Fig. 11—35. Obstruction of the midportion of the transverse duodenum by pancreatitis extending down the mesenteric root. An associated finding is enlargement of the ampulla of Vater.

(Reproduced from Meyers and Evans.2)

Fig. 11-36. Acute pancreatitis with jejunitis.

Besides displacement and mucosal changes in the duodenal loop, evidence of extension of pancreatic enzymes into the small bowel mesentery is shown by their effects on proximal jejunal loops. These demonstrate mucosal edema and sites of spastic narrowing with proximal dilatation.

Duodenal Jejunal Mesentery

Fig. 11-37. Acute pancreatitis.

Jejunitis and ileitis are a consequence of extensive spread of pancreatic enzymes throughout the small bowel mesentery. This is shown by mucosal edema and sites of spastic narrowing with intervening dilatation.

Duodenal Jejunal Mesentery

Fig. 11-37. Acute pancreatitis.

Jejunitis and ileitis are a consequence of extensive spread of pancreatic enzymes throughout the small bowel mesentery. This is shown by mucosal edema and sites of spastic narrowing with intervening dilatation.

Fig. 11—38. Acute pancreatitis.

CT shows infiltration of the mesentery with severe inflammatory changes of the small bowel and colon.

Pneumatosis CecumPneumatosis Treatment

Fig. 11—39. Pneumatosis intestinalis and ischemic changes secondary to pancreatitis.

(a) Plain film shows three grossly abnormal fixed small bowel loops characterized by (1) bubbly gas collections, (2) thumbprinting and edematous mucosa, and (3) markedly effaced or ulcerated mucosa.

(b) Small bowel series. The involved loops show narrowing, ulceration, and pneumatosis.

These features indicate ischemic bowel changes with superimposed pneumatosis. Follow-up 1 month later, following conservative treatment, showed stricture formation in the jejunal segment. (Reproduced from Meyers et al. )

Fig. 11—39. Pneumatosis intestinalis and ischemic changes secondary to pancreatitis.

(a) Plain film shows three grossly abnormal fixed small bowel loops characterized by (1) bubbly gas collections, (2) thumbprinting and edematous mucosa, and (3) markedly effaced or ulcerated mucosa.

(b) Small bowel series. The involved loops show narrowing, ulceration, and pneumatosis.

These features indicate ischemic bowel changes with superimposed pneumatosis. Follow-up 1 month later, following conservative treatment, showed stricture formation in the jejunal segment. (Reproduced from Meyers et al. )

Small Bowel Series

Fig. 11-40. Colonic necrosis complicating traumatic pancreatitis in a 14-year-old male.

(a) Upper GI and small bowel series reveal ischemic changes in the distal small bowel, cecum, and ascending colon. There is a tubular appearance of distal small bowel with loss of mucosal markings, fixation, and separation of loops. The cecum is conical, and there is marked spasm of the ascending colon.

(b) Selective superior mesenteric arteriography demonstrates occlusion of ileocolic branches with intraluminal thrombi (arrow).

Laparotomy showed pancreatitis with widespread fat necrosis and necrosis with perforation of the cecum and ascending colon. Thrombi were identified in the ileocolic artery and mesenteric branches to the ascending colon.

(c) Histologic examination of the hemicolectomy specimen shows two organizing thrombi (arrows) in the submucosal arterial branches and severe venous congestion. Mesenteric veins also showed organized and fresh thrombus formation (hematoxylin-eosin, x 25).

(Reproduced from Dallemand et al.38)

Fig. 11-40. Colonic necrosis complicating traumatic pancreatitis in a 14-year-old male.

(a) Upper GI and small bowel series reveal ischemic changes in the distal small bowel, cecum, and ascending colon. There is a tubular appearance of distal small bowel with loss of mucosal markings, fixation, and separation of loops. The cecum is conical, and there is marked spasm of the ascending colon.

(b) Selective superior mesenteric arteriography demonstrates occlusion of ileocolic branches with intraluminal thrombi (arrow).

Laparotomy showed pancreatitis with widespread fat necrosis and necrosis with perforation of the cecum and ascending colon. Thrombi were identified in the ileocolic artery and mesenteric branches to the ascending colon.

(c) Histologic examination of the hemicolectomy specimen shows two organizing thrombi (arrows) in the submucosal arterial branches and severe venous congestion. Mesenteric veins also showed organized and fresh thrombus formation (hematoxylin-eosin, x 25).

(Reproduced from Dallemand et al.38)

Fig. 11—41. Chronic relapsing pancreatitis with ischemic atrophy of the intestinal mucosa.

The most pronounced changes in this case involve the duodenum and proximal jejunum, which are strikingly abnormal in appearance. The duodenal loop has a dilated moulagelike appearance. The duodenum and loops of jejunum have a tubular toothpaste-like aspect because of the absence of a mucosal relief pattern. Despite the castlike appearance, the involved loops are flaccid and distensible and lack evidence of fixation, rigidity, or thickening. (Reproduced from Meyers and Evans.2)

may then include localized ileus of small bowel loops in the right lower quadrant (Fig. 11-42). This may be a transient, irritative phenomenon. At times, it may portend the development of a pseudocystic collection that can be demonstrated by its displacement of or mass effects upon ileal loops and the cecum (Figs. 11-43 through 11 -45). Since this occurs only with severe pancreatitis, concomitant effects upon other portions of the bowel are usually present. This pathway may be graphically illustrated by CT (Fig. 11-34) or MRI (Fig. 11-46).

Fig. 11—42. Acute hemorrhagic pancreatitis.

Extravasated enzymes passing down the length of the root of the small bowel mesentery produce localized distention of distal ileal loops (arrows) in the right lower quadrant. (Reproduced from Meyers.2)

Imagen Huellas Digitales Radiografia

Fig. 11—43. Acute suppurative pancreatitis.

(a) Admission plain film shows small bowel ileus predominantly in the right lower quadrant (arrow). Note the normal relationship of the stomach (S) and transverse colon (TC).

(b) Barium study 8 days later documents jejunitis and the presence of an exudative abscess displacing distal ileal loops (arrows) at the end of the small bowel mesentery, associated with the development of a large pseudocyst in the tail of the pancreas.

(Reproduced from Meyers and Evans.2)

Fig. 11—43. Acute suppurative pancreatitis.

(a) Admission plain film shows small bowel ileus predominantly in the right lower quadrant (arrow). Note the normal relationship of the stomach (S) and transverse colon (TC).

(b) Barium study 8 days later documents jejunitis and the presence of an exudative abscess displacing distal ileal loops (arrows) at the end of the small bowel mesentery, associated with the development of a large pseudocyst in the tail of the pancreas.

(Reproduced from Meyers and Evans.2)

Fig. 11—44. Acute pancreatitis extending the length of the small bowel mesentery has resulted in a right lower quadrant pseudocystic collection displacing the terminal ileum and cecum (arrows). Changes are also seen in the midtransverse colon near the confluence of the roots of the transverse mesocolon and small bowel mesentery. (Reproduced from Meyers and Evans.2)

Fig. 11-45. Massive right lower quadrant pancreatic pseudocyst causes elevation of cecum and appendix.

Fig. 11—46. Right lower quadrant extension of pancreatic pseudocysts.

(a) Coronal and (b) sagittal Tl-weighted gadolinium-enhanced MR images demonstrate the relationships of three pancreatic pseudocysts (arrows), one of which has localized in the right lower quadrant of the abdomen. (Reproduced from Semelka RC, Ascher SM, Reinhold C: MRI of the Abdomen and Pelvis: A Text-Atlas. Wiley-Liss, New York, 1997, with permission.)

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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