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NBME Surgery Form 1 - Answers & Explanations

Updated: Nov 16, 2019

1) Needle-localized open biopsy • Percutaneous core biopsy, localization with needle and surgically sampling, is preferred for evaluation of microcalcifications • Fine-needle aspiration is inadequate as it may miss the cancer cells

2) Clostridium perfringens • Crepitus = gas-forming = clostridium

3) Lack of normal joint sensation • Neuropathic (Charcot) arthropathy

4) Avascular necrosis of the femoral head • Legg-Calvé-Perthes disease • Common in males between 5-8 years old

5) Low-dose heparin prophylaxis • Heparin is best choice for pre-surgical VTE prophylaxis because it has a short half-life (~45 mins) and is easily reversed with protamine sulfate

6) Cardiogenic shock • SOB, JVD, hypotension, hepatomegaly, ST elevation in anterior leads

7) Surgical decompression • Compartment syndrome

• Paresthesia and pain on passive stretch are early sxs

8) Fat embolism • Associated with long bone fractures and liposuction • Triad: Neurologic dysfunction, petechial rash (usually in axilla), respiratory distress (hypoxemia)

• Therapy is supportive

9) Melanoma • Subungual hematoma, unlike melanoma, will gradually clear as the nail heals

• Subungual hematoma will form a transverse groove across the surface as the nail heals

10) Testicular tumor • Young age, painless progressive enlargement over 8 months = cancer

• Hydrocele and Spermatocele both transilluminate • Epididymitis is painful

11) Appropriate in view of the medical necessity to remove the inflamed appendix

• Acutely inflamed appendix is a medical emergency and therefore doesn’t require consent

12) Ruptured spleen • Kehr sign: referred pain in shoulder due to irritants (eg, blood) in the peritoneal cavity • Kehr sign in the left shoulder is a classic sxs of a ruptured spleen

13) Rapid infusion of 0.9% saline

• Patient is unstable

14) Sphenopalatine artery • Sphenopalatine artery is the MCC of posterior nosebleeds • 90% of nosebleeds are anteriorly located at Kiesselbach’s plexus

15) Ovarian adenocarcinoma

• Nulligravid → uninterrupted menstrual cycles (follicular rupture and tissue damage) → ↑ risk of ovarian cancer

• Advanced ovarian cancer → peritoneal seeding and inflammation → ascites

• Meigs syndrome: triad of ovarian fibroma, ascites, and pleural effusion

16) Increase positive end-expiratory pressure

• Normal PO2 is between 80-10

• FiO2 and PEEP determine PO2; TV and RR determine CO2

17) Slipped capital femoral epiphysis

• Classically presents in teens/pre-teens that are obese or above 90th percentile in weight

18) Incision and drainage of the lesion

• Abscesses must be drained

19) Increased serum aldosterone concentration

• Renin increases on the affected side due to ↓ blood supply → ↑ aldosterone

• Blood supply to unaffected side is normal, so no need to release renin

20) Proctocolectomy with an ileoanal reservoir

• Prophylactic colectomy is the best long-term management in FAP because 100% of cases will eventually progress to CRC

• FAP patients should be screened with a colonoscopy every year starting at age 10-12

21) 15 L of lactated Ringer solution

• Parkland formula: 4 x weight in kg x % area

• 4 x 75 x 50 = 15000 ml = 15L

22) Epidural hematoma • The middle meningeal artery runs underneath the pterion, the weak region of the skull where the frontal, parietal, temporal, and sphenoid bones join together

• Traumatic blows to this area classically cause an epidural hematoma

23) Aortic arteriography

• Mild tenderness over the chest and a ‘somewhat’ widened mediastinum warrant an aortic arteriography

• If the patient had presented with “tearing chest pain radiating to the back” and a widened mediastinum following a MVC, then an immediate thoracotomy would be indicated

24) Carotid duplex ultrasonography

• B/L carotid bruits indicate stenosis in the carotids → compromised blood flow → cerebral ischemia → TIA

• Carotid U/S should be performed to determine the level of stenosis and the corresponding treatment

25) Determination of ankle brachial indices • ABI is the preferred initial step in diagnosis of peripheral arterial disease (PAD)

• Arterial U/S of the lower extremities is less sensitive and specific than ABI for the diagnosis of PAD

26) Vasoactive-inhibitory peptide-secreting tumor

• WDHA: Watery Diarrhea, Hypokalemia, Achlorhydria

• VIPoma is associated with MEN 1 syndrome

• Glucagonomas present with necrolytic migratory erythema, usually in the 5th decade of life

27) Femoral hernia • Protrudes through femoral canal lateral to the pubic tubercle and medial to the femoral vessels

28) Sliding hiatal hernia • Sliding hiatal hernias account for >90% of hiatal hernias • Associated with GERD and reflux esophagitis → ↑ risk of Barrett’s esophagus

29) Cholangitis, ascending • Charcot’s triad: jaundice, fever, RUQ pain • Reynolds pentad: Charcot’s triad, altered mental status, hypotension

• ↑ alkaline phosphatase and ↑ conjugated bilirubin

30) Laparotomy

• Presence of peritoneal signs in a patient with acute abdomen = indication for ex-lap

• Presence of involuntary guarding and rigidity is a contraindication for colonoscopy or sigmoidoscopy

31) Lymphoma

• Lymphatic obstruction (eg, neoplasm) → chylous ascites

32) Failure to suppress class II antigen recognition in the host

• Acute rejection has an onset of weeks to months • CD4 against MHC class II antigen

33) Intravenous administration of calcium gluconate • Hypocalcemia after parathyroidectomy is transient, but IV calcium should be given to protect the heart

34) Lactated Ringer solution

• Ranson’s criteria → pancreatitis

• Tx: fluids, analgesics, NPO

35) Initiation of dialysis

• ↑ urea nitrogen must be corrected pre-operatively because ↑ urea → platelet dysfunction → hemorrhage during surgery

• Demopressin (DDAVP) → ↑ release of factor VIII/vWf multimers, which can correct the coagulopathy in uremic patients

36) RBC 30/hpf (in sediment) • Hematuria, gross or microscopic, occurs in the majority of patients with symptomatic nephrolithiasis

37) Formation of antiplatelet antibodies

• Immune thrombocytopenia (ITP) causes destruction of platelets in the spleen due to anti-GpIIb/IIIa antibodies

• Labs: ↑ megakaryocytes, ↓ platelets

• Treatment: steroids, IVIG, rituximab, splenectomy for refractory cases

38) Water-soluble contrast upper gastrointestinal study • Rupture/perforation is a complication of esophagoscopy • Water-soluble (gastrograffin) contrast study can diagnose rupture

39) CT scan of the abdomen with contrast • Location of injury and gross hematuria suggest kidney injury • Contrast is really excreted and is used to visualize the collecting system

40) Squamous cell carcinoma • SCC → PTHrP → hypercalcemia

41) Aldosteronoma • Hyperaldosteronism → hypokalemia • Aldosterone escape → normal Na levels

42) Bladder outflow obstruction • Old male with mass in lower quadrant indicated BPH

43) Gastric bypass

• This patients has comorbidities due to morbid obesity (she is most likely bed-ridden → poor personal hygiene)

• BMI > 35 with a major comorbidity (eg, HTN, DM, etc.) qualifies for bariatric surgery; BMI > 40 qualifies without the presence of comorbidities

44) Heparin-induced thrombocytopenia • Antibody-heparin-PF4 complex activates platelets → thrombosis and thrombocytopenia

45) Thoracic spinal cord • Breast cancer metastasis to spinal cord • Decreased sensation below T4 indicates a thoracic location

46) Pseudomonas species

• Gram negative rod

47) Malignant pleural effusion • Past hx of cancer, respiratory distress, cyanotic, cachectic, decreased breath sounds, dullness to percussion • Pleural friction rub could be due to post-radiation fibrosis of the lungs

48) Atrial myxoma • Obstruction of mitral valve in diastole → diastolic murmur

• Changing of positions → movement of tumor → disappearance of murmur

• Cardiac myxoma produce IL-6 → fever and weight loss

49) Cytomegalovirus • Colitis in HIV + nuclear inclusion bodies = CMV • Presents with hematochezia, abdominal pain, weight loss, low-grade fever

50) High-output congesting heart failure • Circulatory overload → ↑ diastolic pressure in LV → pulmonary edema

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