1. Resident on call small bowel obstruction and beyond on radiograph: all about the pattern of bowel gas
Yuyang Zhang, Darko Pucar, Janet Munroe, Norman B. Thomson, Jayanth Keshavamurthy
Department of Radiology, Medical college of Georgia of Augusta University
Introduction
Small bowel obstruction (SBO) is a common radiographic scenario the on call resident encounters at night. The differential diagnosis is broad which include congenital, intrinsic, extrinsic bowel disease and luminal occlusion, four gross categories and many variants. Based on the abdominal radiograph the residents, especially the new on call residents, are under tremendous stress to decide how to triage the patient. Depending on the etiology of the SBO, the treatments of small bowel obstruction and pseudo-obstruction are quite different which include simply observation, nonsurgical including nasogastric tube suction or emergent surgery. The selection of treatment relies on quick and accurate diagnosis.
Case 2: 31 years old male with sudden onset 10/10 abdominal pain. On radiology, all the bowel gas is seen on the right and none on the left, concerning for malrotation. The contrast CT shows dilation of small bowel, absence of contrast enhancement and swirling sign of the mesentery, consistent with malrotation. During surgery, the small bowel is noted to be non-viable, malrotated around SMA. Nearly complete small resection was performed. The plain film finding of midgut malrotation with ischemic bowel may include double bubble sign or isolated gas-containing loop of bowel distal to the obstructed duodenum. The right side only distribution of bowel gas in this case should raise the alarm of midgut malrotation. (arrow=swirling sign)
Case 4: 64 years old female with history of multiple myeloma presents with abdominal distention, pain, nausea and vomiting. On radiograph and CT, markedly dilated small bowel is noted. An ultrasound image of the small bowel is also shown which demonstrate echogenic thickened bowel wall. Biopsy of the bowel shows amyloidosis. Multiple subsequent radiograph and CT in a long term show unchanged pattern of bowel gas. Gastrointestinal amyloidosis is rare and can be confused with small bowel obstruction. CT findings include bowel wall thickening and contrast retention. Amyloidosis of SB may be hypo-vascular on US and hypermetabolic on PET. Without appropriate treatment, the imaging finds will be constant. Repeat CT to exclude SBO of these patients with known GI amyloidosis should be avoided.
Case 6: 47 years old male with history of gallstone present with abdominal pain. Radiograph of the abdomen shows small bowel distension with air-fluid levels concerning for SBOs. On CT, a 3.4 x 3.6 cm stone is seen in the terminal ileum concerning for gallstone ileus. After conservative treatment, spontaneous pass of gallstone occurred with resolution of bowel distention. Gallstone ileus is a type of mechanical obstruction. Care must be taken in finding the gallstone, as only a minority are calcified (12.5%). Density may be similar to bowel content. (arrow=large gallstone)
Small bowel obstruction cases
Conclusion
Obtaining CT for every patient presenting with abdominal pain and dilated small bowel is neither reasonable nor rational given the cost and radiation. Good history and comparison to previous examinations are necessary to narrow the differential. However, in a hectic call night of a resident a thorough research of history and previous exams is too time-consuming and unlikely to happen. We believe it is essential for a resident to learn to recognize the different patterns of bowel gas on screening radiograph in conjunction with available history, physical and pertinent imaging to facilitate the decision-making. We expect that the study of gas pattern of these pathologies on radiograph with correlation of confirmation exams will help resident to boost their skill on complicated SBO cases on radiograph.
Case 3: 23 years old female without significant past medical history presents with 5 days of abdominal pain. The initial diagnosis was gastroenteritis in outside hospital. The radiograph shows small bowel distention suspicious for SBO. The over night read of contrast CT from resident is SBO without transitional zone. The final read of attending next AM called acute thrombosis of SMV and portal vein with concern of bowel ischemia. During surgery, non-viable proximal bowel was resected. Acute SMV thrombosis is uncommon, accounting for only 5-15% of all cases of acute mesenteric ischemia. Radiographic finding of bowel ischemia is non-specific. Ileus pattern with dilated, fluid filled loops of bowel may been seen. Thumb-printing, separation of bowel loops, pneumatosis or portal venous gas may occasionally seen[Bradbury 2002, radiographics]. (Arrow=thrombosis in SMV)
Case 1: 61 years old male with history of ulcerative colitis and recurrent SBOs presents with abdominal pain and distention. On the radiograph there is dilated featureless bowel on the left measuring up to 7 mm. No definite narrowing or transitional zone. Per patient’s chart, patient had total colectomy after development of toxic megacolon. The dilated loop of bowel is actually small bowel. SBO is a common complication after proctocolectomy. Most of them are caused by adhesion. A differential diagnosis is paradoxical anal muscle contraction.
Case 5: 32 years old male post appendectomy three days ago presents with abdominal pain, nausea and vomiting. The plain film shows marked dilation of small bowel and small amount of bowel gas in the colon. The finding is favored to represent ileus and unlikely SBO. Post surgical ileus was diagnosed by CT with visualization of passage of oral contrast into colon and without appreciation of transitional zone. Patient’s symptom initially improved after nasogastric tube decompression. However, a repeat CT 1 week later after deterioration of symptoms demonstrated multiple intra-abdominal abscesses. Ileus is the paralysis of intestine without mechanical obstruction. Some degree of ileus is expected after abdominal surgery. However, prolonged ileus (>72 hrs) is suggestive of complication, such as obstruction, perforation, peritonitis or abscess. (arrows=abscess)