Preguntas y Respuestas 7

Cirugía General

A 23-year-old man is admitted to the hospital through the emergency department with probable appendicitis. He has been having right lower quadrant abdominal pain for several days, which has been becoming increasingly worse. His temperature 39.2 C (102.6 F), blood pressure is 80/40 mm Hg, pulse is 120/min, and respirations are 35/min. The abdomen is rigid with guarding. Multiple petechiae and purpura are present, and the patient is oozing blood from his oral mucosa. According to the patient's wife, he has not had bleeding problems in the past.

 Question 1 of 5.  The fact the abdomen is rigid with guarding suggests which of the following?

/ A. Colon cancer

/ B. Diverticulitis

/ C. Liver failure

/ D. Peritonitis

/ E. Shock

The correct answer is D. The usual reason for a patient to have a rigid abdomen is that peritonitis is present, and is causing severe pain related to peritoneal nerve fiber stimulation. The probable cause of the peritonitis is a ruptured appendix. This patient is also probably in shock (choice E), as indicated by the hypotension with increased respirations and heart rate, but this would not cause the abdominal guarding. The other answers are distracters.

Question 2 of 5.  Given this patient's presentation, which of the following is the most likely cause of his petechiae, purpura, and mucosal blood oozing?

A. Disseminated intravascular coagulation

B. Hemophilia A

/ C. Idiopathic thrombocytopenic purpura

/ D. Von Willebrand disease

/ E. Wiskott-AIdrich syndrome

The correct answer is A. You should suspect disseminated intravascular coagulation (DIC) in patients who are seriously ill with other disease who then develop evidence of a coagulopathy. In this case, sepsis is the probable inciting event.

DIC is thought to occur in 30-50% of patients with sepsis, and may, in many cases, be triggered by a reaction to gram-negative or staphylococcal cell wall material. Other settings in which DIC can be a complication include major trauma, obstetric complications, acute myelocytic leukemias, disseminated carcinomas, burns, massive transfusions, acute hepatic failure, myocardial infarction, and inflammatory conditions (e.g., ulcerative colitis, rheumatoid arthritis, Crohn disease, sarcoidosis).

Question 3 of 5. Which of the following findings on screening laboratory tests would be most consistent with the probable diagnosis?

/ A. Decreased platelet count, increased prothrombin time, increased activated partial thromboplastin time

/ B. Increased platelet count, increased prothrombin time, normal activated partial thromboplastin time

/ C. Increased platelet count, normal prothrombin time, increased activated partial thromboplastin time

/ D. Normal platelet count, increased prothrombin time, increased activated partial thromboplastin time

/ E. Normal platelet count, normal prothrombin time, normal activated partial thromboplastin time

The correct answer is A. Platelet count is invariably decreased (and usually obvious on peripheral smear) in DIC, and this is one of the more reliable screening tests for the condition (although it does not exclude many other diagnoses). Both prothrombin time and activated partial thromboplastin times are often prolonged, but you should be aware that they might each be shortened or normal as well in DIC. Thus, these two commonly performed tests are actually not as useful as they might appear. The other choices listed are wrong because the platelet counts are not decreased.

Question 4 of 5. For confirmation of the probable diagnosis, the emergency department physician orders a D-dimer test. D-dimer is which of the following?

/ A. A clotting factor in the common coagulation pathway

/ B. A clotting factor in the extrinsic coagulation pathway

/ C. A clotting factor in the intrinsic coagulation pathway

/ D. A factor found in the complement pathway

/ E. A fibrin degradation product

The correct answer is E. One of the more available and useful of these tests is the D-dimer tests, which measures a fibrin degradation product that is made when a cross-linked clot (indicating the presence of thrombin to form the clots) is lysed by plasmin. One way to understand disseminated intravascular coagulation is to think of it as primarily a thrombotic problem, with excessive clot formation and then lysis, which leads secondarily to a hemorrhagic problem as platelets and clotting factors are consumed. High D-dimer levels indicate that clots are forming and then lysing at an unusual rate in the body, and thus, together with a low platelet count, suggest that DIC is present.

Question 5 of 5. Which of the following would be most effective in diminishing the rate at which clot formation is occurring?

/ A. Aminocaproic acid

/ B. Heparin

/ C. PIatelet transfusion

/ D. Red cell transfusion

/ E. Tranexamic acid

The correct answer is B. The patients are often already critically ill, and the DIC they have developed often contributes to major organ failure. The basic problem in therapy is how to treat simultaneous bleeding and clotting tendencies. Paradoxically, while the bleeding tendency may be appearing to dominate the clinical picture, treatment with the anticoagulant heparin may actually help the patient by decreasing the rate at which the clotting factors are being consumed. This must, of course, be done very carefully, since an "overshoot" may exacerbate the patient's problems.

A 25-year-old woman consults a physician because she has developed severe dysphagia and constipation that has led to a recent weight loss of 15 pounds. She is referred to a gastroenterologist, to whom she reports that she has a great deal of trouble swallowing solid foods, but not Iiquids, and has also been having nearly constant gastroesophageal reflux symptoms. She has awakened during the night several times coughing and feeling as if she had aspirated acid stomach contents. Esophagogastroduodenoscopy and colonoscopy are performed, and demonstrate massive dilatation of the esophagus and colon.

Question 1 of 5. Which of the following parasitic diseases would most likely produce megaesophagus and megacolon?

/ A. Chagas disease

/ B. Cysticercosis

/ C. Hydatid disease

/ D. Malaria

/ E. Threadworm infection

The correct answer is A. Megaesophagus and megacolon are unusual pathologic changes, and should bring Chagas disease to mind, which is also known as American trypanosomiasis. Megacolon, but not megaesophagus, can also be due to Hirschsprung disease, but this is usually diagnosed in infants and young children and is due to abnormal neural development in the gut.

Question 2 of 5. The infecting species is which of the following?

/ A. FIuke

/ B. Nematode

/ C. PIasmodia

/ D. Tapeworm

/ E. Trypanosome

The correct answer is E. Chagas disease is caused by infection with Trypanosoma cruzi, which is an intracellular protozoan parasite that takes a leishmanial form within muscle cells.

Question 3 of 5. On further questioning, the woman reports having lived for a year in Bolivia as a teenager. At one point, she had had an automobile accident and had been transfused with blood at a local hospital there. The person whose blood she received had probably acquired the infection via a bite by which of the following?

/ A. FIea

/ B. Mosquito

/ C. Reduviid bug

/ D. Tick

/ E. Tsetse fly

The correct answer is C. Reduviid bugs are insects that live in poorly constructed adobe housing and feed on human or animal blood. Trypanosomes they ingest during their feedings multiply in the insect gut and are deposited in fecal material near the wound when the insect bites another individual. Contamination through the wound leads to invasion into, and reproduction within, host cells. Release of the trypanosomes back into the blood stream makes them available for transmission either via another bug bite or via blood transfusion. While Chagas disease can persist for decades, the period in which significant numbers of parasites are in the blood is usually only during the comparatively short (and often asymptomatic) acute phase of the illness.

Question 4 of 5. While this woman's gastrointestinal tract disease brought her to medical attention, involvement of which of the following is the principal source of morbidity and mortality in this condition?

/ A. Heart

/ B. Kidneys

/ C. Liver

/ D. Lungs

/ E. Pancreas

The correct answer is A. Chagas disease is conventionally divided into three stages. The short acute period may be asymptomatic or may be characterized by fever, swelling of lymph glands, hepatosplenomegaly, and local inflammation at the site of the bite. This is followed by an asymptomatic period, which may last years to the rest of the patient's life. In one-third of patients, clinically evident disease becomes apparent 10-20 years after infection. 27% of infected patients develop cardiac symptoms (which may cause flaccid cardiomyopathy, cardiac aneurysm formation, or sudden death); 6% develop digestive system damage with megaviscera (thought to be related to neural involvement rather than muscle involvement); and 3% develop neural involvement. You should also be aware that coexisting AIDS infection may predispose for an unusually rapid and severe course of Chagas disease.

Question 5 of 5. While no drug therapy is useful in the therapy of chronic cases, treatment can be used in newly diagnosed acute cases. Which of the following medications would be most useful in treating the acute infection?

/ A. Chloroquine

/ B. Doxycycline

/ C. Nifurtimox

/ D. Primaquine

/ E. Pyrimethamine-sulfadoxine

The correct answer is C. The diagnosis in suspected acute cases can be established with review of thin or thick blood smears. (The diagnosis in latent and chronic cases usually requires special blood culture techniques or PCR-amplified detection of parasite DNA in blood.) The only effective drugs are nifurtimox and benznidazole, which are given in courses up to 4 months because the organisms are difficult to eradicate. The other choices listed are drugs used in malaria prophylaxis or treatment.

A 65-year-old man presents to his physician because he has been having increasing difficulty swallowing over the past 2 months. He is still able to swallow liquids, but swallowing solid food now causes severe pain and a sense of fullness behind his sternum. He has lost 18 pounds since his swallowing difficulties began. The patient is referred to a gastroenterologist, who demonstrates a mass lesion of the distal esophagus, which on biopsy is shown to contain cancer.

  Question 1 of 6.  Which of the following is most important in separating the esophagus from the larynx, and must consequently be carefully passed behind during endoscopy?

/ A. Arytenoids

/ B. Cricoid cartilage

/ C. Epiglottis

/ D. Pharynx

/ E. Vocal cords

The correct answer is C. Endoscopists are very careful when guiding the endoscope past the epiglottis, which is a pear-shaped portion of elastic cartilage that can be moved during swallowing to close the larynx, preventing swallowed material from eventually entering the lungs.

Question 2 of 6. Which of the following nerves provides the efferent impulses necessary for the esophageal actions that occur during swallowing?

/ A. GIossopharyngeal

/ B. Hypoglossal

/ C. Spinal accessory

/ D. Trigeminal

/ E. Vagus

The correct answer is E. The vagus nerve supplies the efferent input into the esophagus that is necessary for swallowing.

Question 3 of 6. Which of the following approximately represents the proportion of different esophageal cancer types now being observed in the United States?

/ A. 1/10 adenocarcinoma and 9/10 squamous cell carcinoma

/ B. 1/3 adenocarcinoma and 2/3 squamous cell carcinoma

/ C. 1/2 adenocarcinoma and 1/2 squamous cell carcinoma

/ D. 2/3 adenocarcinoma and 1/3 squamous cell carcinoma

/ E. 9/10 adenocarcinoma and 1/10 squamous cell carcinoma

The correct answer is C. More recent statistics indicate that the incidence of adenocarcinoma and squamous cell carcinoma of the esophagus are now roughly equal. Formerly, approximately 2/3 of the esophageal cancers were squamous in origin (choice B). Adenocarcinoma of the esophagus is often found in the distal esophagus.

Question 4 of 6. Precancerous metaplasia of the esophageal epithelium gives rise to a mucosa resembling which of the following?

/ A. Mesothelium

/ B. Respiratory epithelium

/ C. Small intestine

/ D. Squamous epithelium

/ E. Stomach

The correct answer is C. This is an indirect question about Barrett's esophagus, which is an important precursor of adenocarcinoma of the esophagus. While Barrett's esophagus was initially defined to be either gastric-type or intestinal-type metaplasia of the esophagus, more recent studies have shown that the actual problem lesion is more likely to be intestinal metaplasia (diagnosed when isolated goblet cells are seen in the epithelium) rather than gastric metaplasia (choice E).

Question 5 of 6. Frequent use of which of the following has recently been found to probably have a protective effect against development of esophageal cancer?

/ A. Acetaminophen

/ B. AIcohol

/ C. Aspirin

/ D. Cigarettes

/ E. Codeine

The correct answer is C. An interesting new research observation that may be exploited in the future is that the incidence of esophageal cancer appears to be much lower in people who use aspirin frequently.

Question 6 of 6. Currently, esophageal cancer has which of the following long-term survival rates?

/ A. Less than 5%

/ B. 30%

/ C. 50%

/ D. 70%

/ E. More than 95%

The correct answer is A. Esophageal cancer is one of the very bad cancers, presently with poor long-term survival. The underlying problem is that the esophagus is only about 3 mm thick, and both metastatic disease and direct spread (often unresectable) to mediastinal structures is common. Active research is presently being undertaken to modify this prognosis by using chemotherapy and radiation therapy prior to surgery, but these modalities have not yet come into widespread use.