Exercise: Intestinal Distention

EXERCISE 8-4. INTESTINAL DISTENTION

8-13. What is the most likely diagnosis in Case 8-13 (Figure8-25)?

A.   Functional ileus of the bowel

B.   Mechanical obstruction of the colon

C.   Mechanical obstruction of the small bowel

D.   Pneumoperitoneum

8-14. What is the most likely diagnosis in Case 8-14 (Figure8-26)?

A.         Functional ileus of the bowel

B.         Gastric outlet obstruction

C.         Mechanical obstruction of the small intestine

D.         Pneumoperitoneum.

8-15. What is the most likely cause of the distended bowel loop (arrowheads) in Case 8-15 (Figure 8-27)?

A.         Cecal volvulus

B.         Functional ileus of the bowel

C.         Pneumoperitoneum

D.         Sigmoid volvulus.

8-16. What is the most likely diagnosis in Case 8-16 (Figure8-28)?

A.         Ascites

B.         Functional ileus of the bowel

C.         Mechanical obstruction at the colon

D.         Mechanical obstruction at the small bowel.

Radiologic Findings

8-13. In this case, a diffuse abnormal gas pattern with dis-tention of the small bowel, colon, and rectum sug-gests functional ileus. Two days later the patient underwent laparotomy, and small-bowel ischemia was found (Figure 8-29) (A is the correct answer to Question 8-13). Separation of bowel loops may indi-cate bowel wall thickening but is a nonspecific sign.

8-14. This case shows gaseous distention of the stomach, duodenum, and jejunum on the supine film, but no gas is seen in the colon, suggesting mechanical small-bowel obstruction. Gastric outlet or duode-nal obstruction is unlikely because many jejunal loops are dilated. At surgery, an obstructing jejunal adhesion was found (C is the correct answer to Question 8-14).

8-15. This patient has a huge distended and folded colonic loop in the midabdomen and pelvis (the “coffee bean” sign). The most likely consideration is a sigmoid volvulus (D is the correct answer to Question 8-15).

8-16. This case shows distended transverse colon and de-scending colon and no gas in the sigmoid colon and rectum. The small bowel is not distended. Mechani-cal obstruction of the colon distal to the level of de-scending colon is likely (C is the correct answer to Question 8-16). Barium enema (Figure 8-30) showsan irregular narrowing at the rectosigmoid region, indicative of sigmoid carcinoma.

Discussion

Generalized or diffuse distribution of gas, both in the small bowel and in the colon, is more indicative of a functionalileus. The most common causes of functional ileus are post-operative status, neuromuscular diseases, ischemia, and in-trinsic or extrinsic inflammations. Air-fluid levels may be seen in patients with functional ileus when plain films are ob-tained with the patient in upright or decubitus position.

Limited distribution of abnormal gas in the intestine fa-vors a mechanical obstruction. Air-fluid levels may also be seen in patients with mechanical obstruction when an up-right abdominal radiograph is obtained. The most com-mon causes of mechanical obstruction in the small bowel are adhesions, internal or external hernias, neoplasms, or intussusceptions. Ileocolic intussusception is common in children.

When the small bowel is filled with a large amount of fluid, a row of small gas bubbles may be trapped between the valvulae conniventes. The row of gas bubbles is called the “string of beads” or “string of pearls” sign and is seen on the decubitus or upright view of the abdomen (Figure 8-31). A fluid-filled, closed-loop small bowel obstruction may appear as an oval mass in the abdomen and is known as the “pseudo-tumor sign” (Figure 8-32). These signs suggest a mechanical obstruction and possible strangulation.

Sigmoid volvulus may twist along the mesenteric axis and the long axis of the bowel. The twisted and overdis-tended sigmoid colon may appear as an inverted U shape or a coffee bean shape, without haustra or septa, at the upperpelvis and abdomen crossing the transverse colon. The colon above the sigmoid may be distended; however, the small bowel is rarely distended in a patient with sigmoid volvulus. Barium enema may show a beaking sign adjacent to the twisted point. Vascular insufficiency may occur if volvulus cannot be corrected.

A small-bowel volvulus may be caused by internal hernia or adhesion similar to that of sigmoid volvulus. Small-bowel volvulus may be located outside the pelvis with no proximal colonic dilatation. Cecal volvulus is the cause of 1% to 2% of intestinal obstructions. Most often a cecal volvulus is twisted and relocated in the midabdomen or left upper quadrant (Figure 8-33).

Mechanical obstruction of the colon is commonly caused by colonic neoplasm, volvulus, or inflammatory mass caused by diverticulitis of the left colon. All colonic segments proxi-mal to the mechanical obstruction are distended with gas or a combination of gas and feces. When intestinal secretions and fecal matter fill the distended bowel loop, solid and liquid contents produce a mottled appearance. Whether the small bowel becomes distended from a colonic obstruc-tion depends on its duration and severity, and also on the competency of the ileocecal valve. Abdominal radiographs are often of limited value in differentiating the cause of bowel distention, and CT is more useful for locating a mechanical obstruction (Figure 8-34).