Which type of enema is typically used to relieve constipation by instilling and retaining fluid for a short period before expelling?

Rationale:

A. Used to visualize the upper gastrointestinal tract (esophagus, stomach, duodenum). It does not provide information about bowel obstruction in the large intestine.

B. Allows direct visualization of the colon mucosa but is not typically used initially in suspected acute bowel obstruction due to the risk of perforation.

C. Useful for evaluating gallbladder, liver, kidneys, and sometimes bowel, but it is less sensitive for detecting large bowel obstruction.

D. A plain abdominal X-ray (KUB) is often the first-line diagnostic study for suspected large bowel obstruction. It can show dilated bowel loops, air-fluid levels, and fecal loading, which correlate with the patient’s symptoms of bloating, distention, and relief after flatulence.

Rationale:
A. Vomiting is more common in small bowel obstruction and is usually less severe in large bowel obstruction.

B. A large bowel obstruction causes accumulation of gas and fecal material proximal to the blockage, leading to significant abdominal distention.

C. Large bowel obstruction may eventually cause metabolic acidosis due to impaired perfusion and tissue hypoxia, not alkalosis.

D. Back pain is not a typical sign of large bowel obstruction; the primary symptom is abdominal discomfort, distention, and constipation.