Answers

1. c—More than 80% of cases of coumadin-induced skin necrosis occur on medication days 3-7, although the condition has been reported to occur far later than that. The most commonly involved areas are the buttocks, legs, and breasts. Since this is not an infectious disease, antibiotics are not helpful, nor are they indicated. Coumadin-induced skin necrosis is associated with protein C deficiency and is, paradoxically, a thrombotic disorder. This rare complication has a prevalence of 0.01%-0.1%.
    
2. e—Although follicular carcinoma cannot compete with normal thyroid tissue for iodine, in the absence of a thyroid, this carcinoma can concentrate iodine; that is the principle which supports the use of radioactive iodine for scanning and treatment after total thyroidectomy. Psammoma bodies occur in papillary carcinoma. Follicular carcinoma is not commonly bilateral (papillary carcinoma is), and it spreads by the vascular route, rarely involving lymph nodes. Fine needle aspiration cytology can identify the presence of follicular cells but cannot distinguish benign (adenoma) from malignant (carcinoma); these investigations are characterized as indeterminate.
    
3. c—The obturator nerve innervates the adductor longus and gracilis muscles. It originates from lumbar nerves 2-4. It traverses the psoas muscle and provides sensation to the medial thigh. It has no role in anal sphincter control.
    
4. b—The only lesion that is NOT involved in the von Hippel-Lindau syndrome is melanoma.
    
5. a—Grade III lacerations create intraparenchymal hematomas > 5 cm. Capsular tears 1-3 cm deep and subcapsular hematomas involving 10%-50% of the surface area are grade II, while involvement of the hilar vessels represents grade IV. Active hemorrhage is not part of the grading system and could occur in any stage. There is a direct relationship with grade and the likelihood of hemorrhage, which occurs rarely in grade I and almost always in grade IV.
    
6. a—The rate of development of symptoms is 3% annually; thus, the majority of patients remain symptomatic for more than 10 years. Similarly, the rate of complications is 3%-5% per year, so considerably fewer than 90% develop them. Most asymptomatic patients do not need cholecystectomy; the major indications for operation in asymptomatic patients are diabetes, isolation from medical care, candidacy for transplantation, and old age. Cholelithiasis is a definite risk factor for carcinoma of the gallbladder. More than 30% of patients with cholelithiasis have bacteria on bile culture; the defense mechanisms are lost due to stasis and the decreased concentrations of bile salts, which are bacteriostatic.
    
7. c—Esophageal perforation during diagnostic and therapeutic endoscopic procedures is by far the most common cause. Among the remainder, Boerhaave's syndrome accounts for 15%, foreign bodies for 14%, trauma for 10%, and carcinoma for < 1%.
    
8. b—Most colonic diverticula are false diverticula, in which the mucosa and submucosa herniate through the colonic wall near the entrance of the vessels at the teniae coli. Diverticula cause hemorrhage in < 5% of cases and inflammation in 20%-25% of patients. They are most common in the sigmoid colon and are due to increased intraluminal pressure during evacuation of stools that are too small because of the absence of dietary fiber.
    
9. b—The pubococcygeus is the most anterior of a series of muscles that are critical in maintaining the integrity of the pelvic floor and preventing the development of cystoceles and rectoceles; it forms the lateral border of the urogenital hiatus. The puborectalis is too far posterior and the levator ani is too far posterior and superficial (it constitutes the anal sphincter). The ischiocavernosus runs along the bony pelvis; it contains some erectile elements. The transverse perinei are far more superficial and create the perineal body.
    
10. d—Sestamibi scanning is more than 85% reliable in localizing parathyroid adenomas. It is the study of choice for localization after failed parathyroidectomy or recurrent hyperparathyroidism. Cinacalcet is an excellent calcium-lowering agent, but it is indicated only in patients who are not surgical candidates. Even without a serum parathyroid hormone level, the low serum phosphorus is diagnostic of hyperparathyroidism; if the patient was hypercalcemic from metastatic malignancy, the phosphorus would be high or normal. Neck exploration without preoperative localization runs a very high risk of failure, particularly since there is a 25% chance that the adenoma would be in the mediastinum. Venous sampling studies are effective but invasive; they should be used only when Sestamibi fails to localize the lesion.
     
11. b—The incidence of complications of Meckel's diverticula in adults is so small (< 1%) that unless it is symptomatic, causing diverticulitis or hemorrhage, or contains a mass, it should not be resected. If a Meckel's diverticulum is resected, for an appropriate indication, the specimen should include an adjacent section or segment of normal small intestine.
     
12. c—Since fibroadenomas are benign and have a miniscule risk of malignant transformation, there is no reason to remove them if the diagnosis is known. Since the diagnosis is generally easy to make on fine needle aspiration cytology, resection is rarely indicated. Neither size nor symptoms are indications.