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The correct answer is C) Surgical wound dehiscence.
This patient presents with peritonitis (“acute abdomen”) – one of the classic “tests” to verify this presentation is to bump the patient’s bed without warning or strike the bottom of their feet. The patient’s presentation, recent transvaginal surgery, and, most importantly, her X-ray clinch this diagnosis, which would later be confirmed with a gynecological examination revealing communication between the vaginal vault and the patient’s pelvis. The X-ray shows a striking amount of free air under the patient’s diaphragm (pneumoperitoneum), which indicates visceral perforation (as seen in small bowel obstructions & volvulus) or direct communication with the external environment.
A) Pyelonephritis is incorrect because one would expect this patient to have urinary symptoms and complain of flank or back pain. Fever, nausea, and vomiting are all consistent with this presentation, so it would be considered on the initial differential.
B) Metastatic cancer is incorrect because the rate of basal cell cancer metastasis is extremely low (~0.03%).
D) Fitz-Hugh-Curtis syndrome should be on the initial differential – it is a rare complication of pelvic inflammatory disease (PID) in which ascending infection causes the liver capsule to become inflamed. Though the patient denies vaginal discharge, PID/FHC is still a possibility as it would present in a similar fashion. Pneumoperitoneum is not expected in FHC – a more consistent presentation is right upper quadrant abdominal pain that may be referred to the shoulder (Kehr’s sign) exacerbated by breathing, palpation, or movement.
E) Gastroenteritis is incorrect because it is inconsistent with the given history, and uncomplicated gastroenteritis should not cause acute peritonitis.
F) Drug overdose is incorrect because the patient does not display signs of narcotic/opiate toxicity on exam. However, in a patient with a known history of substance abuse, one must always consider the possibility of drug effects or the consequences thereof. Conceivably, this patient could have developed endocarditis from IV drug abuse and thrown septic emboli to the mesenteric vessels, resulting in ischemia and bowel perforation, which would account entirely for this presentation – this is not the most likely explanation, however, but serves to illustrate the importance of keeping a differential diagnosis open.
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