A 17-year-old boy is taken to the emergency department because he has developed severe abdominal pain. The pain began abruptly several hours previously, and was felt initially in the periumbilical region, but later shifted to the right lower quadrant. The boy had initially felt somewhat nauseous, but this has passed. On physical examination, he is noted to have localized pain on cough and to be running a low-grade fever.
Q 1
Examination of the abdomen demonstrates right lower quadrant tenderness at the junction of the middle and outer thirds of the line joining the umbilicus to the anterior superior spine of the iliac. This location is known as which of the following?
/ A. Gubernaculum
/ B. Langer's line
/ C. Linea alba
/ D. McBurney's point
/ E. Tunica albuginea
Q 2
Which of the following is the most likely diagnosis?
/ A. Appendicitis
/ B. Diverticulitis
/ C. Gallstones
/ D. Rectal ulcer
/ E. Renal colic
Q 3
The patient also exhibits an increase in pain in the right lower quadrant from the passive extension of the right hip joint. This finding suggests that the inflammation also involves which of the following?
/ A. BIadder
/ B. External oblique muscle
/ C. Femur
/ D. IIiopsoas muscle
/ E. Transverse abdominal muscle
Q 4
The patient is prepared for immediate surgery. Cefotaxime is administered before, during, and after surgery. The specimen, once removed, is sent to the laboratory for pathology and bacteriologic culture. A malodorous pus surrounds the serosa of the surgical specimen, and a mixed gram-negative flora is cultured. Rapid enzyme tests for beta-Iactamase production are positive. Which of the following drugs should be added to the initial cefotaxime regimen?
/ A. Bacitracin
/ B. CIavulanic acid
/ C. CIindamycin
/ D. Isoniazid
/ E. Vancomycin
Q 5
The patient's postoperative recovery is uneventfuI, but 10 days after discharge, he returns to his physician complaining of continuous low-grade fever. An abscess is drained transrectally, and organisms are cultured from the pus. Which of the following is an attribute of this organism that makes it an important abscess former?
/ A. It is an anaerobe
/ B. It is an intracellular pathogen
/ C. Its endotoxin lacks 2,3-ketodeoxyoctonate
/ D. Mycolic acid
/ E. Prodigious capsule
Abdominal Pain Case 5 Answers
A1
The correct answer is D. The point described is McBurney's point, which overlies the location of the appendix in most individuals.
The gubernaculum (choice A) is the fibrous cord that connects the primordial testis or ovary to the anterolateral abdominal wall.
Langer's lines (choice B) are the cleavage lines of the skin.
The linea alba (choice C) is a sheet-like aponeurosis that covers the anterior abdominal wall.
The tunica albuginea (choice E) is a tough fibrous coat that covers the testis.
A2
The correct answer is A. This patient has a typical presentation for appendicitis, and the diagnosis is confirmed by the presence of localized tenderness at McBurney's point.
Diverticulitis (choice B) is usually a disease of middle-aged or older individuals and most commonly affects the left-lower quadrant.
Symptomatic gallstone disease (choice C) causes pain and tenderness in the right upper quadrant.
Rectal ulcer (choice D) causes pain with stool movement, but does not usually produce tenderness identifiable on abdominal examination.
Renal colic (choice E) usually produces flank or lower back pain.
A3
The correct answer is D. This patient has a "positive psoas sign," which is an increase in pain from passive extension of the right hip joint. This maneuver stretches the iliopsoas muscle, which lies behind the appendix and can become secondarily inflamed when the appendiceal inflammation extends through the serosa. The psoas sign is clinically useful in both confirming the appendix as the probable origin of the patient's pain, and indicating that the inflammation is transmural and that the risk of rupture and peritonitis is increased.
The bladder (choice A) is located more medially, and is usually not affected by appendicitis.
The external oblique (choice B) and transverse abdominal (choice E) muscles are in the anterior and lateral abdominal walls, and do not usually become inflamed with appendicitis.
The femur (choice C) is moved during the extension of the right hip joint, but is not the source of the pain.
The correct answer is B. Clavulanic acid is a beta-lactamase inhibitor, which when administered with beta lactam agents, irreversibly binds and inactivates bacterial beta-lactamases, thereby permitting the companion drug to disrupt bacterial cell wall synthesis. Suspected appendicitis is usually treated with prompt appendectomy, since delay is associated with increased risk of potentially life-threatening peritonitis and sepsis.
Bacitracin (choice A) is not correct, since this drug inhibits bacterial cell wall synthesis by binding to and inhibiting the dephosphorylation of a membrane-bound lipid pyrophosphate. Gram-negative bacteria are resistant to this agent, and it would not have a synergistic effect if administered with a third generation cephalosporin.
Clindamycin (choice C) is not correct, because this drug blocks protein elongation by binding to the 50S ribosome. Although it is effective against anaerobic gram-negative bacilli, it would not have a complementary effect when administered with a third generation cephalosporin.
Isoniazid (choice D) is not correct because it inhibits the synthesis of mycolic acids for the cell wall of actively dividing Mycobacteria. It would not be effective in the flora of this patient's gut, nor would it act synergistically with third generation cephalosporins.
Vancomycin (choice E) is not correct because it disrupts cell wall synthesis in growing gram-positive bacteria. It would not be effective against the flora of this patient's gut, nor would it act synergistically with third generation cephalosporins.
The correct answer is E. Prevotella (Bacteroides) is a frequent cause of abscesses in the intestinal tract because it is a normal flora organism and produces a large capsule, which impedes phagocytosis.
Although the genus is anaerobic (choice A), it is not this attribute which causes its formation of abscesses.
Prevotella is extracellular, not an intracellular pathogen (choice B).
Although Prevotella does indeed have this type of endotoxin (choice C), the absence of this molecule decreases the toxicity of the toxin, and does not contribute to its proclivity toward abscess formation.
Mycobacteria, and not other genera such as Prevotella, are known for their long-chain fatty acids (mycolic acids; choice D).
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ReplyDeleteThanks a lot for this awesome post.
Smith Alan