WBR0931
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology |
| Sub Category | SubCategory::Gastrointestinal |
| Prompt | [[Prompt::A 26-year-old woman is admitted to the emergency room for severe right lower quadrant pain. On physical exam, she has a positive McBurney’s sign and CT scan with oral and IV contrast confirms the diagnosis of appendicitis. She undergoes emergency appendectomy. Her postoperative course is complicated by persistent, diffuse abdominal pain, with palpable distension. She is unable to tolerate an oral diet due to nausea and vomiting on ingestion. Despite the feeling of bloating she has not passed any flatus up to postop day 5. Upright abdominal X-rays are negative for signs of bowel obstruction. Which of the following pharmacotherapies may help treat this patient’s condition?]] |
| Answer A | AnswerA::Bethanechol |
| Answer A Explanation | AnswerAExp::Correct: Bethanechol is a cholinomimetic agent that can be used to treat postoperative ileus and urinary retention. |
| Answer B | AnswerB::Erythromycin |
| Answer B Explanation | AnswerBExp::Incorrect: While erythromycin can increase intestinal motility, it is ineffective in the setting of postoperative ileus. (Smith et al. 2000) |
| Answer C | AnswerC::Neostigmine |
| Answer C Explanation | [[AnswerCExp::Incorrect: Neostigmine is a cholinesterase inhibitor that can be used to reverse neuromuscular junction blockade and treat myasthenia gravis. It is ineffective for the treatment of postoperative ileus (Myrhoj et al. 1988) *Note: First Aid is out-of-date on this.]] |
| Answer D | AnswerD::Carbachol |
| Answer D Explanation | AnswerDExp::Incorrect: Carbachol is a cholinomimetic drug (CARBon copy of acetylcholine). Carbachol eyedrops are used to decrease the pressure in the eye for people with glaucoma. It is sometimes used to constrict the pupils during cataract surgery. |
| Answer E | AnswerE::Methacholine |
| Answer E Explanation | AnswerEExp::Incorrect: Methacholine is an inhaled non-selective muscarinic receptor agonist used in “challenge tests” to diagnose bronchial hyperreactivity (asthma and COPD). |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Postoperative ileus should be suspected when a patient has nausea/vomiting, abdominal distension and failure to pass flatus for at least 3-5 days following abdominal surgery. Before making the diagnosis of postoperative ileus, bowel obstruction must be ruled out. Postoperative ileus is thought to occur due to inflammation caused by surgical manipulation of the bowel.
The muscarinic receptors in the bladder and gastrointestinal tract stimulate contraction of the bladder and expulsion of urine, and increased gastrointestinal motility, respectively. Bethanechol is a cholinomimetic agent that can be used to treat postoperative ileus and urinary retention. It should be used to treat these disorders only after mechanical obstruction is ruled out as a possible cause. Educational Objective: Bethanechol is a cholinomimetic agent that can be used to treat postoperative ileus and urinary retention. References: First Aid 2012 page 265 First Aid 2013 page 233 Smith AJ, Nissan A, Lanouette NM, Shi W, Guillem JG, Wong WD, Thaler H, Cohen AM. Prokinetic effect of erythromycin after colorectal surgery: randomized, placebo-controlled, double-blind study. Dis Colon Rectum. 2000;43(3):333. PMID 10733114 Myrhöj T, Olsen O, Wengel B. Neostigmine in postoperative intestinal paralysis. A double-blind, clinical, controlled trial. Dis Colon Rectum. 1988;31(5):378. PMID 3284726 |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Bethanechol, WBRKeyword::Postoperative, WBRKeyword::Postoperative ileus, WBRKeyword::IIeus, WBRKeyword::Gastroparesis, WBRKeyword::Gastric motility |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |