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Q1: What does the small bowel enema show (see p 627)?
The small bowel enema shows normal jejunum. The ileum is shortened in its distal portion and uniformly narrowed with a smooth outline; the ileocaecal junction is well delineated and the caecum is normal.
Q2: What is the differential diagnosis?
The differential diagnosis of ileal stricture includes tuberculosis, Crohn’s disease, pelvic inflammation, ischaemia, radiation enteritis, carcinoid infiltration, lymphoma, and diffuse enteropathy—that is, disorders where there is inflammation, infiltration, or oedema of the small bowel. History and clinical findings in this case did not contribute to the diagnosis.
Q3: How can you confirm the diagnosis?
Enteroscopy/terminal ileoscopy is the investigation of choice. In active Crohn’s disease, the terminal ileum shows patchy asymmetrical and heterogenous mucosal lesions. Ulcers which may be aphthoid, superficial, or deep are seen surrounded by normal mucosa. Tuberculoid granuloma is the most specific finding on histology apart from infiltration of lamina propria by lymphocytes and plasma cells with aggretates of lymphocytes near the base of the crypts. In the present case, the smooth and featureless mucosa, and inflammatory cellular infiltrate of lamina propria suggests Crohn’s disease in remission. The patient has not been on any medication for over four years.
Segmental areas of luminal narrowing of ileum referred to as ileal stricture is due to rigid thickening and fibrosis of its wall resulting in obstruction. It is a common complication of Crohn’s disease, tuberculosis, and intestinal ischaemia. A flare-up of inflammatory process causes temporary intestinal narrowing; when healing occurs with a scar or fibrous tissue formation the obstruction is complete. The narrowing could either be circumferential and concentric or eccenteric and irregular in nature. On barium contrast examination, these strictures typically appear as segmental narrowing without normal mucosal pattern and with smooth tapered ends—referred to as the “string sign”. Strictures themselves are painless and may not require treatment. But sometimes, these areas become so narrow and result in a partial or total obstruction.
What is the pathophysiology of stricture formation? The intestine can propel the lumenal contents only when the lumen remains fairly wide enough. When there is damage to the intestinal mucosa due to inflammation, the smooth muscle cells of the intestine activate a complex chain of events, involving a host of immune system components, for example, interleukin-1β. There is production and deposition of more than normal collagen at the site of injury. Scarring occurs, the layers of intestinal muscle thicken, and the muscles no longer move smoothly and easily. In short, a stricture forms, compromising the intestine’s ability to function efficiently.
An important differential diagnosis of ileal stricture in the present case is Crohn’s disease, based on the peroperative findings of mesenteric thickening and ileal stricture at enteroclysis. A featureless outline of a diseased ileal segment, due to atrophy of the folds from long standing inflammation, is not an uncommon finding in Crohn’s disease.1 In one series this was seen in 29% of cases2; the biopsy is not likely to be helpful in these situations. Crohn’s disease is being increasingly reported from India.3 It is today included as an important differential diagnosis for ileal tuberculosis. The strictures are caused by shrinkage of a tuberculous ileocaecal mass to form a fibrous constriction. In a country where both problems exist, distinction becomes difficult. Non-response to antituberculosis treatment favours the diagnosis of Crohn’s disease. The patient has not been treated for tuberculosis.
In Crohn’s disease, like tuberculosis, the small intestine is the most common affected site (80%).1 In the early stages of the disease, the narrowing is due to oedema and spasm; with progression of the disease, fibrosis manifests as a lumenal narrowing. These findings are also seen in tuberculosis. Few radiological signs are specific for Crohn’s disease. These include fissures, ulcers, sinuses, fistulae, and asymmetrical involvement, skip lesions, and long longitudinal ulcers. Less specific findings include luminal narrowing, stricture formation, and dilatation proximal to stenosis, thickening of the mucosal folds, cobblestoning, discrete ulcers, or mural thickening. Long segmental narrowing of the terminal ileum was the only positive finding in the present case.
Khwaja and Subbuswamy reported ischaemic strictures of the small intestine from northern Nigeria.4 The radiological features are non-specific and simulate tuberculosis and Crohn’s disease. Even at laparotomy, it may be difficult to differentiate this from Crohn’s disease and tuberculosis. Hypotensive drugs can occasionally produce intestinal ulceration and stricture formation.5
The barium infusion technique (enteroclysis) is an ideal investigation for study of the small intestine, both for focal lesions and for extensive mucosal disease. In the best of hands, the procedure gives an optimal radiological-gross pathological correlation and satisfactory evaluation of the extent, depth of the disease, and complications.6
A histological difference between Crohn’s disease and tuberculosis is not always possible. Supportive information only helps in making a diagnosis. In the case reported, the peroperative findings of ileal stricture resembled Crohn’s disease and ileal tuberculosis; terminal ileoscopy and histology was not helpful. The possible diagnosis is Crohn’s disease in “remission”.
The patient under study has been asymptomatic for four years and is not on any medication. Intervention in ileal strictures is necessary when an individual is symptomatic. Steroids, aminosalicylic acid preparations, immunomodulators, and verapamil have been used during the inflammatory phase; the latter inhibits the smooth muscle cells’ response to intestinal injury and prevents collagen deposition. When the affected segment is fibrosed and scarred, endoscopic balloon dilatation can relieve the obstruction. Surgical options include stricturoplasty and resection of the affected segment.
Crohn’s disease in “remission”.