A 32-year-old female presents with a 6-week history of bloody diarrhea, abdominal pain, andurgent bowel movements. On examination, she is found to be pale and has mild tenderness in the lower abdomen. Laboratory investigations reveal an elevated C-reactive protein (CRP), and stool cultures are negative for infections. The clinical presentation strongly suggests inflammatory bowel disease (IBD). What is the most meaningful investigation for confirming the diagnosis of ulcerative colitis?
A. Barium enema
B. Sigmoidoscopy with biopsy
C. Proctoscopy
D. Stool culture
E. Blood culture
Correct Answer: B. Sigmoidoscopy with biopsy
Explanation:
Ulcerative colitis (UC) is a chronic inflammatory condition that primarily affects the mucosal layer of the large intestine, starting at the rectum and extending proximally. The diagnosis is confirmed through a combination of clinical features, endoscopic examination, and histopathology. Among the options provided, sigmoidoscopy with biopsy is the most meaningful and definitive investigation to confirm the diagnosis of ulcerative colitis.
Why Sigmoidoscopy with Biopsy is the Best Investigation:
- Direct Visualization of Colonic Mucosa:
- Sigmoidoscopy allows direct visualization of the rectum and sigmoid colon, where ulcerative colitis typically begins. The characteristic findings in UC include continuous mucosal inflammation, ulceration, and erythema that starts in the rectum and extends proximally.
- Biopsy for Histological Diagnosis:
- A biopsy taken during sigmoidoscopy is crucial for confirming the diagnosis. Histopathological findings in UC include:
- Inflammation limited to the mucosa.
- Crypt abscesses (neutrophils within the crypts).
- Basal plasmacytosis and crypt distortion.
- These features help differentiate UC from other forms of IBD, such as Crohn’s disease, which affects the full thickness of the bowel wall and typically has a discontinuous pattern of inflammation.
- A biopsy taken during sigmoidoscopy is crucial for confirming the diagnosis. Histopathological findings in UC include:
- Most Effective for Diagnosis:
- Sigmoidoscopy with biopsy is considered the gold standard for diagnosing ulcerative colitis because it directly examines the affected area and provides tissue for histological confirmation.
Analysis of Other Options:
A. Barium enema:
- A barium enema can be useful for visualizing the colon and can show features suggestive of UC, such as loss of haustral markings and mucosal irregularities. However, it is less specific than endoscopy and does not provide tissue for biopsy. This test is now less commonly used due to the availability of more sensitive and specific diagnostic tools like colonoscopy or sigmoidoscopy.
C. Proctoscopy:
- A proctoscopy allows for the examination of the rectum but does not extend to the sigmoid colon or beyond. While it may reveal inflammation in the rectum, it is not sufficient for a complete diagnosis of UC, as the disease typically involves the entire colon. Sigmoidoscopy is preferred because it allows evaluation of the sigmoid colon and can be performed with a biopsy.
D. Stool culture:
- Stool cultures are important for diagnosing infectious causes of diarrhea, such as bacterial infections (e.g., Salmonella, Shigella) or parasitic infections. However, in the context of suspected ulcerative colitis, stool cultures are typically negative. UC is a non-infectious inflammatory bowel disease, and stool culture is not a diagnostic tool for UC.
E. Blood culture:
- Blood cultures are used to detect systemic infections, especially bacteremia, but they are not relevant in the diagnosis of ulcerative colitis. While UC can cause complications like toxic megacolon or sepsis (which may warrant blood cultures), blood cultures alone will not help diagnose UC.
Clinical Presentation of Ulcerative Colitis:
- Symptoms:
- Bloody diarrhea (often with mucus).
- Abdominal pain (usually in the lower abdomen).
- Urgency, with a feeling of needing to have a bowel movement frequently.
- Weight loss, fever, and fatigue in more severe cases.
- Signs:
- Tachycardia, hypotension (in severe cases).
- Tenderness in the lower abdomen.
- Pale appearance due to anemia (a common complication of UC).
Management of Ulcerative Colitis:
- Medical Treatment:
- Aminosalicylates (e.g., mesalamine) for mild to moderate disease.
- Corticosteroids for flare-ups and more severe disease.
- Immunosuppressive agents (e.g., azathioprine, methotrexate) for long-term control of moderate to severe disease.
- Biologic therapies (e.g., TNF inhibitors, vedolizumab) for severe or refractory cases.
- Surgical Management:
- Surgery may be necessary in cases of toxic megacolon, perforation, or uncontrolled disease. A colectomy with or without ileal pouch-anal anastomosis (IPAA) is the typical procedure for severe cases.
Summary:
Ulcerative colitis (UC) is a chronic inflammatory condition affecting the colon, and sigmoidoscopy with biopsy is the most meaningful and definitive investigation for diagnosing this condition. Sigmoidoscopy allows direct visualization of the rectum and sigmoid colon, revealing characteristic mucosal changes, while biopsy provides histopathological confirmation. Although tests like barium enema, proctoscopy, and stool cultures may have a role in certain scenarios, they are less specific than sigmoidoscopy with biopsy for confirming UC. Early diagnosis and appropriate treatment, including aminosalicylates, immunosuppressive therapies, and sometimes surgery, are essential for managing UC and improving patient outcomes.