Preguntas y Respuestas 2

CIRUGÍA GENERAL

• After suitable calculations have been made using the modified Parkland formula, a 70-kg man with extensive third-degree burns is receiving Ringer's lactate at the calculated rate, which happens to be 750 mL/hr. The infusion was started within 30 minutes of the time when the burn occurred. Over the next 3 hours, his urinary output is recorded as 15 mL, 22 mL, and 18 mL. It is verified that the Foley catheter is open and draining freely. The urine is dark yellow, without blood, and has a specific gravity of 1040 and a sodium concentration of 10 mEq/L. The patient's blood pressure is 100/70 mm Hg, his pulse is 98/min, and his central venous pressure is 2 cm H2O. On the basis of these findings, which of the following is the most appropriate next step in management?• A. Diuretics should be given• B. Fluid administration should continue at the present rate• C. The rate of fluid administration should be decreased• D. The rate of fluid administration should be increased• E. Treatment is needed for renal failure

• Explanation:• The correct answer is D. The calculations made by standard formulas

are only an educated guess. Once fluid administration begins, we judge its adequacy by the information provided by urinary output and central venous pressure, aiming for an output of 1-2 mL/kg/hr, while not exceeding a venous pressure of 10 or 15. In this case, our calculations fell short of the mark, and the patient needs more fluids at a faster rate.

• A 47-year-old man presents to the emergency room with sudden onset of severe upper abdominal pain with vomiting. The pain is focused in the epigastrium with radiation to the back. Serum amylase levels are 2000 U/L. Which of the following are the most commonly encountered predisposing factors for this patient's condition?• A. Alcohol use and gallstones• B. Helicobacter pylori infection and excess gastric acid secretion• C. Hepatitis B infection and iron overload• D. Obesity and high serum cholesterol• E. Stress and cigarette use

• Explanation:• The correct answer is A. The clinical scenario is typical of acute

pancreatitis. The overwhelmingly most important contributing factors for development of acute pancreatitis are gallstones (particularly small ones) and alcohol abuse.

• A 25-year-old man experiences the gradual onset of intermittent diarrhea, which over years, progresses to severe diarrhea, alternating with constipation, rectal bleeding, and passage of mucus. On physical examination, the abdomen is tender over the colon. Stool examination fails to reveal parasites. Colonoscopy demonstrates inflammation limited to the rectum, with no higher lesions. Which of the following diseases would most likely be seen in a close relative of the patient?• A. Celiac disease• B. Crohn's disease• C. Hirschsprung's disease• D. Tropical sprue• E. Whipple's disease

• Explanation:• The correct answer is B. The presentation is classic for ulcerative

colitis. Family members have an increased incidence of both ulcerative colitis and Crohn's disease, supporting the idea that these two diseases are actually different ends of the same spectrum. In contrast to Crohn's disease, in which the lesions may be patchy and involve the distal ileum and even the esophagus, in ulcerative colitis, the lesions involve the rectum and may extend continuously proximally for varying distances up to the cecum and very distal end of the ileum.

• A 54-year-old woman with chronic microcytic hypochromic anemia also has a sore, smooth, red tongue and a sense of dysphagia midway during swallowing. This patient is at increased risk for developing which of the following conditions?• A. Adenocarcinoma of the esophagus• B. Barrett's esophagus• C. Candida esophagitis• D. CMV esophagitis• E. Squamous cell carcinoma of esophagus

• Explanation:• The correct answer is E. The patient has Plummer-Vinson syndrome,

characterized by atrophic glossitis, esophageal webs, and iron-deficiency anemia. Patients with this syndrome are at increased risk of developing squamous cell carcinoma of the esophagus.

• A 56-year-old alcoholic man is brought in to the emergency room after being found unconscious by his daughter, who called the paramedics. Paramedics report finding the man in a stuporous condition in the bathtub, covered with vomit. On arrival to the emergency room, the man is clammy and his blood pressure is 85/50. Which of the following conditions is the most likely cause of his hypotension?• A. Acute hemorrhagic pancreatitis• B. Chronic calcifying pancreatitis• C. Chronic obstructive pancreatitis• D. Cystic fibrosis• E. Pancreatic pseudocyst

• Explanation:• The correct answer is A. Acute hemorrhagic pancreatitis is a life-threatening

abdominal emergency that is most often seen in the setting of excessive acute alcohol or food ingestion. In this condition, activated Pancreatic enzymes are released into the tissues, where they cause severe local damage to the pancreas, with pain radiating to the back. The enzymes are also released into the blood stream. Shock may result from hemorrhage, activation of bradykinin and related peptides, and/or release of proteolytic and lipolytic enzymes into the circulation. Other systemic manifestations include hypocalcemia, glucose intolerance, and jaundice.

• A 35-year-old woman complains of severe lower abdominal pain, which is worst during menstruation. Laparoscopic examination of the pelvis demonstrates multiple small brown spots on the surface of pelvic structures. Most of these lesions are cauterized, but biopsy of one of the remaining lesions reveals glandular tissue resembling normal endometrium. No cytologic atypia or abnormally shaped glands are seen.• Which of the following is the most likely diagnosis?• A. Acute endometritis• B. Adenomyosis• C. Chronic endometritis• D. Endometriosis• E. Metastatic endometrial cancer

• Explanation:• The correct answer is D. Endometriosis is defined as a benign growth

of endometrium at sites at which it does not normally Occur (excluding the myometrium, at which site it is called adenomyosis). Endometriosis is common and is a significant cause of both pain and pelvic scarring. Most of the problems occur because the abnormally located endometrium responds to hormonal control and may menstruate, producing a very irritating fluid. Endometriosis may apparently be started either by seeding of menstrual cells in the pelvis (entering through the open end of the fallopian tubes) or by metaplasia of mesothelial or other cells (accounting for rare, welldocumented cases of endometriosis of bizarre sites such as nasal mucosa or lungs).

• A 48-year-old woman is seen by a clinician. She has a bright red, sharply demarcated, oozing and crusting rash involving one breast in the areola area. She has had this lesion for six months and states that it is slowly growing. The lesion does not respond to antibiotic ointment, antifungal ointment, or steroid ointment. This lesion is most likely related to which of the following conditions?• A. Breast cancer• B. Crohn disease• C. Gastric cancer• D. Rheumatoid arthritis• E. Systemic lupus erythematosus

• Explanation:• The correct answer is A. This is Paget disease of the breast, which

actually corresponds microscopically to the presence of individual adenocarcinoma cells in the epidermis. When it involves the nipple area, it usually overlies an area of breast cancer. (Paget disease can also involve the vulva and vagina, where it may be unrelated to bulk cancer.) It is important to recognize the presentation, since focusing on treating the skin lesion empirically can lead to a delay in recognizing the cancer. The clinical description given in the question stem is typical. Mastectomy is a common form of treatment in these cases because of the nipple involvement.

• A 49-year-old woman has a firm, 2-cm mass in the right breast that has been present for 3 months. Mammogram has been read as "cannot rule out cancer," but it cannot diagnose cancer either. A fine-needle aspiration of the mass (FNA) and cytology do not identify any malignant cells. Which of the following is the most appropriate next step in management? • A. Reassurance and reappointment in a year• B. Repeat mammogram and FNA in 1 month• C. Core or incisional biopsies• D. Lumpectomy and axillary dissection• E. Modified radical mastectomy

• Explanation:• The correct answer is C. Negative findings do not have the same

diagnostic value that positive findings have. If this had been a 19-year-old woman suspected of having a fibroadenoma, one would have been satisfied with negative imaging studies (in that age, a sonogram) or the negative FNA. But, at age 49, the risk of cancer is much higher. Given negative findings in the least invasive studies, one would feel compelled to move to more aggressive ways to obtain better tissue sampling.

• A 56-year-old man has been having bloody bowel movements on and off for the past several weeks. He reports that the blood is bright red, it coats the outside of the stools, and he can see it in the toilet bowl even before he wipes himself. When he does so, there is also blood on the toilet paper. After further questioning, it is ascertained that he has been constipated for the past 2 months and that the caliber of the stools has changed. They are now pencil thin, rather the usual diameter of an inch or so that was customary for him. He has no pain. Which of the following is the most likely diagnosis?• A. Anal fissure• B. Cancer of the cecum• C. Cancer of the rectum• D. External hemorrhoids• E. Internal hemorrhoids

• Explanation:• The correct answer is C. The combination of red blood coating the

stools and a change in bowel habit and stool caliber spells out cancer of the rectum in someone in this age group.

• A 34-year-old perfume saleswoman presents complaining of lower abdominal cramps and diarrhea. She has no prior history of gastrointestinal illnesses and began noting frequent loose stools 3 days earlier. The stools have subsequently become bloody and associated with urgency and nocturnal bowel movements. She has also developed an increased temperature of 38.4 C (101.1 F). On examination, she has mild periumbilical and left lower quadrant tenderness. On rectal examination, the stool is bloody. Which of the following organisms is most likely causing her symptoms?• A. Campylobacter jejuni• B. Cryptosporidium• C. Giardia lamblia• D. Staphylococcus aureus• E. Toxigenic Escherichia coli

• Explanation:• The correct answer is A. Campylobacter jejuni is a common cause of

community-acquired bloody diarrhea. It is acquired via the fecal-oral route and may produce a non-bloody or bloody diarrhea. If the symptoms are as severe as in this patient, antibiotics (e.g., ciprofloxacin) would be appropriate.

• A 19-year-old man consults a physician about a 2 cm neck mass. The patient has no systemic symptoms at that time. The mass is resected and proves to be a lymph node showing replacement of normal follicles by sheets of a mixed population of cells including histiocytes, lymphocytes, moncytes, plasma cells, and eosinophils. Scattered large binucleate cells are also seen. These cells are positive for CD15 and CD30 on immunohistochemical staining. Which of the following is the most likely diagnosis?• A. Burkitt lymphoma• B. Hairy cell leukemia• C. Hodgkin disease• D. Mycosis fungoides• E. Waldenstrom macroglobulinemia

• Explanation:• The correct answer is C. This patient has Hodgkin disease. The large

binucleate cells are Reed-Sternberg cells. Immunohistochemical confirmation of these cells is important, because, despite the apparently distinctive appearance of Reed-Sternberg cells in textbooks, "lookalike“ cells with very similar appearance can be seen in a variety of situations. Hodgkin disease has a bimodal age distribution with one peak in late adolescence-young adulthood and a second peak in older individuals. Systemic symptoms are usually not initially prominent, and these patients tend to be identified either when a neck mass is evaluated or when a chest x-ray performed for other reasons demonstrates mediastinal lymphadenopathy.

• A 68-year-old woman presents with an obviously incarcerated umbilical hernia. She has gross abdominal distention, is clinically dehydrated, and reports persistent fecaloid vomiting for the past 3 days. Although tired, weak, and thirsty, she is awake and alert and her sensorium is not particularly affected. Laboratory analysis reveals a serum sodium concentration of 118 mEq/L. Which of the following is the most likely physiologic explanation for the serum sodium?• A. She has acute water intoxication• B. She has been vomiting and trapping hypertonic fluids in the bowel lumen• C. She has vomited and sequestered sodium-containing fluids, and has retained• endogenous and ingested water• D. There must be a laboratory error, because such a serum sodium level would

have produced coma• E. Volume deprivation leads to renal wasting of sodium

• Explanation:• The correct answer is C. Gastrointestinal tract fluids have a sodium

concentration very close to that of plasma; as they are lost (internally or externally), they should be replaced with isotonic, sodium-containing fluids. But that is not what patients typically do at home. Thirsty and unable to eat solid (sodium-containing) foods, they drink water, Coke, and tea, fluids without significant amounts of sodium, which the body avidly retains because of the severe volume depletion. Endogenous water from catabolic activity is also retained. Dilutional hyponatremia eventually develops.

• Durante una laparoscopia realizada por otras razones, el cirujano identifica un hígado de coloración obscura muy uniforme. ¿Cual es el diagnóstico mas probable?• A. Angiosarcoma• B. Síndrome de Dubin-Johnson• C. Hemocromatosis• D. Melanoma maligno• E. Enfermedad de Wilson

• Respuesta correcta B• El Síndrome de D-J es una hiperbilirrubinemia conjugada hereditaria

que causa una coloración oscura en el hígado. EL origen de la pigmentación no esta bien esclarecido. El defecto genético conduce a una alteración en la transportación canalicular generando significantes cantidades de bilirrubina no conjugada en la sangre derivadas de la desconjugación de la bilirrubina en el sistema hepatobiliar

• Un masculino de 79 años, con dolor en el cuello al tragar. Ocasionalmente regurgita comida sin digerir poco después de comer. Cual es el diagnostico mas probable?• A. Desgarro de Mallory-Weiss• B. Síndrome de Pummer-Vinson• C. Anillos de Schatzki• D. Divertículo por tracción• E. Divertículo de Zenker

• Respuesta correcta E• Es una presentación clásica del divertículo de Zencker, el cual es un

falso divertículo que se hernia a través de la mucosa en un punto débil de la faringe y el esófago en la pared posterior de la hipofaringe. También esta asociado con halitosis, causa disfagia y obstrucción esofágica.

• Femenino de 35 años, se presenta a la consulta con dificultad para la deglución a los solidos y a algunos líquidos durante los últimos años. El medico sugiere que estos hallazgos pueden tener relación con una condición autoinmune. Cual de las siguientes hallazgos puede reforzar el diagnostico?• A. Rash en mariposa• B. Boca seca• C. Tiroides grande• D. Piel gruesa• E. Nódulos en la lengua

• Respuesta correcta D• La escleroderma (esclerosis sistémica progresiva) causa también

engrosamiento de la dermis por deposito de colágeno. Lo mismo sucede con el esófago que envuelve los dos tercios distales del esófago.