NBME Surgery Form 3 - Answers & Explanations

Updated: Nov 16, 2019

1) Malignant hyperthermia

• Malignant hyperthermia can occur up to 12 hours after exposure to causative drug

• Fever, encephalopathy, unstable vitals, “lead pipe” muscle rigidity

2) Inhibited synthesis of prostacyclin

• Ketorolac (NSAID) inhibits the vasodilatory properties of prostacyclin → constriction of afferent arterioles → renal failure (↑ creatinine)

3) Biliary atresia

• Initially well-appearing followed by jaundice and conjugated hyperbilirubinemia over the next 1-8 weeks

• Dx: Ultrasound showing absent or abnormal gallbladder; gold standard is intra-operative cholangiogram showing biliary obstruction

• Tx: Kasai procedure (hepatoportoenterostomy) or liver transplant; Biliary atresia is the most common indication for pediatric liver transplantation

• Breast milk jaundice would present with unconjugated hyperbilirubinemia

4) Crohn disease

• “String sign” on barium x-ray = thin luminal contrast, usually in terminal ileum from spasm and eventual fibrosis

• ~50% of patients present with a palpable abdominal mass, usually in the RLQ

5) Sarcoidosis

• B/L hilar adenopathy, course reticular infiltrates, often asymptomatic

6) Bacterial overgrowth

• Decreased gastric acid/motility → bacterial overgrowth

• Tx: antibiotics (hence improvement with tetracycline)

7) CT scan of the abdomen and kidneys

• Emergent surgery is not warranted as there are no alarm signs

• Imaging should be performed to evaluate the type of management she requires

8) Insulinoma

• Whipple triad

• Increased C-peptide = endogenous source

9) Rapid administration of 500 mL of 0.9% saline

• Water challenge test - give 500 mL of normal saline, if the patient can urinate and post void volume is normal than it was dehydration. However if no urine is produced then its acute renal failure

10) Complication of right atrial catheter

• Hickman line = central venous catheter most often used for administration of chemo

• Complications of Hickman line include hemorrhage and pneumothorax during insertion.

• Complications at later stages include thrombosis and infection - the line should be regularly flushed with saline to prevent blood clots/blockage

• This patient has engorgement of veins, no arteries (arterial embolism)

11) Myocardial infarction • Cardiogenic shock: cold/clammy, tachycardia, hypotension, increased PCWP

12) C8 • No loss of reflex; Biceps C5, C6 and Triceps C6, C7 • C8 Ulnar nerve is responsible for sensation in the ring and pinky finger

13) Craniotomy • Chronic subdural hematoma → urgent surgical evacuation of symptomatic or large bleeds

14) Esophagoscopy and biopsy • Alarm sxs → must rule out cancer with endoscopic biopsy

15) Observation • Topical silver sulfadiazine therapy can be used for partial/full thickness burns

16) Carotid stenosis

• Multiple Hollenhorst plaques indicates possible embolism from carotid stenosis leading to amaurosis fugax

• Carotid duplex identifies degree of lumen narrowing

• Black rim = peripapillary atrophy, a common incidental finding that is irrelevant in this case

• Diabetic retinopathy is insidious, not acute

• Glaucoma would also be insidious with a high cup to disc ratio (this patients ratio is normal)

17) Mitral stenosis • Opening snap with late diastolic rumbling

18) Ectopic pregnancy • Cornual pregnancy = ectopic pregnancy in the interstitial portion of fallopian tube invading through the uterine wall

19) Intravenous administration of fluids • Mallory-Weiss tear with hypotension secondary to multiple bouts of bloody emesis

20) Pilonidal abscess • Common in young males at the superior gluteal cleft

21) Pulmonary contusion • Parenchymal bruising of the lung → intra-alveolar hemorrhage and edema • Commonly after blunt thoracic trauma → tachypnea, tachycardia, and hypoxia • Physical exam: ↓ breath sounds and chest wall bruising • Dx: CT shows patchy irregular alveolar infiltrate (may not show up right away on CXR)

• Tx: pain control, supplemental oxygen

22) Surgical exploration of the right femoral artery

• Comminuted fracture = break or splintering of bone into > 2 fragments

• Absent popliteal, tibial and DP pulses (which all arise from the femoral artery) - femoral artery should be explored to see where it was damaged

• In traumatic injuries, bone should be fixed first, then vascular injuries, and finally nerve injuries; reduction of bone may displace and damage vascular structures which is why is should take place first

23) Exploratory laparotomy • Although this patient only has a hematocrit of 15% and normally wouldn’t be operated on, the presence of rebound tenderness (peritonitis) and absence of bowel sounds indicated the necessity for surgery

24) Patent ductus arteriosus • Continuous machine like murmur

25) FEV1 • DLCO or FEV1 provide the best estimate of post-op morbidity

• DLCO or FEV1 < 40% → moderate/high risk of post-op morbidity

• Normal FEV1 is ~4L in males, ~3L in females

26) Renal cell carcinoma • Classic triad: painless hematuria, flank pain, abdominal mass

• PTHrP → hypercalcemia and hypophosphatemia

27) Exploratory thoracotomy • Boerhaave syndrome → surgical repair

28) Renal artery stenosis

• RAS = narrowing of renal arteries most often caused by atherosclerosis or fibromuscular dysplasia

• Smoking and angina indicate underlying atherosclerotic disease

• Fibromuscular dysplasia is more common in females

29) Thrombocytopenia • Patient only received pRBCs → dilution of platelets

• Larger transfusions require a 1:1:1 ratio of pRBCs, platelets, plasma

• In general, once you administer the 4th pRBC, a unit of platelets should be given

30) Antithrombin III deficiency • Recurrent clots in a young patient with no inciting event = hereditary thrombosis syndrome leading to hyper-coagulability

31) Splenectomy

• First-line treatment of ITP is steroids and IVIG

• Refractory ITP should be treated with splenectomy to prevent further destruction of platelets

32) E