David DiSantis

Journal Club: Prevalence of flawed multiple-choice questions in continuing medical education activities of major radiology journals.

OBJECTIVE The purpose of this study was to assess whether the continuing medical education (CME) multiple-choice questions (MCQs) in three major radiology journals adhere to standard question-writing principles. MATERIALS AND METHODS All CME MCQs (total of 181) in the January 2013 editions of the AJR, RadioGraphics, and Radiology composed the test sample. Each question was evaluated by three reviewers for compliance with seven MCQ-writing guidelines that have been documented in the medical education literature as associated with frequent flaws in medical CME. RESULTS Seventy-eight of the 181 (43%) questions contained one to four flaws. CONCLUSION A large fraction of radiology CME questions violate standard question-writing principles.

The comb sign.

20 years ago, Abdominal Imaging editor Morton Meyers described a CT sign now firmly in the radiology lexicon. He observed that, on contrast enhanced CT, the parallel engorged mesenteric vessels that supply bowel afflicted with active Crohn’s disease resemble the parallel teeth of a comb (Fig. 1). Thus, the ‘‘Comb Sign’’ was born. The sign is thought to reflect acute exacerbation of Crohn’s Disease, showing straightening and dilation of the vasa recta to the inflamed bowel segment. The vessels are separated by mesenteric fat proliferation, a presumed response to more chronic inflammation (Fig. 2) [1].

The bowel wall target sign.

Traditionally, a target configuration describes concentric circles [1]. So when CT depicts abnormally thickened bowel wall as concentric rings of varying attenuation, the imaging appearance has been dubbed the target sign (Fig. 1) [2]. On intravenous contrast enhanced CT without positive enteric contrast material (Fig. 2 a, b), the target sign comprises three rings of alternating attenuation. Two high attenuation value rings—mucosa (inner ring) and muscularis propria (outer ring)—are separated by low attenuation value submucosa (middle ring), presumably reflecting edema or fat [3, 4]. As a differential diagnostic consideration, while the sign is associated with bowel wall thickening of varied etiology (infection, inflammation, ischemia, shock bowel, and radiation), it generally does not occur in neoplasia [5].

The hyperattenuating ring sign of acute epiploic appendagitis

Epiploic appendages are small fat-containing pouches that protrude from the serosal surface of most of the colon. Usually, the normal epiploic appendages are not visible on CT, though adjacent ascites can reveal them (Fig 1). Epiploic appendages are pedunculated, mobile, and supplied by an end artery. With torsion of an appendage, acute ischemia can produce fat necrosis, inflammation, and localized peritoneal irritation. The condition, termed epiploic appendagitis (EA), occurs more commonly on the left side [3], mimicking the symptoms of acute diverticulitis. As might be expected, right-sided EA can

Coffee bean sign

The coffee bean sign is a metaphor describing the classic radiographic appearance of a closed loop obstruction, most notably associated with sigmoid volvulus [1, 2]. Twisting of the sigmoid colon about its mesenteric axis creates an inverted, U-shaped, and a gas-filled segment of dilated bowel originating in the pelvis and extending cephalad. A central linear opacity bisects the dilated loop (Fig. 1a), mimicking the cleft of a coffee bean (Fig. 1b). This central line represents the ‘‘double’’ thickness of apposed bowel walls [3] (Fig. 2). Failure to recognize this finding may lead to delayed diagnosis with increased risk of ischemia, infarction, and perforation. Emergent operation for sigmoid volvulus has been associated with 24% mortality, compared with 6% in an elective setting [4].

‘Tardus-Parvus’ waveform

Vascular complications after orthotopic liver transplant are a major source of morbidity and mortality. Doppler ultrasound is useful as a screening modality, and with prompt diagnosis followed by angioplasty/stenting, patient mortality and graft-loss rates are minimal [1]. Termed ‘‘Tardus-Parvus’’ (Late-weak), the characteristic spectral tracing of hepatic arteries in cases of significant proximal stenosis, or proximal occlusion with collateralization, demonstrates a late-arriving systolic peak, with diminished peak systolic amplitude, and a low resistive index [2] (Figs. 1, 2 and 3). Tardus refers to the late-arriving systolic peak, and parvus the decreased peak amplitude.

The “double bubble” sign

The classic radiographic appearance of duodenal atresia—a gas-filled stomach with simultaneous dilated gasfilled proximal duodenum—has long been referred to as the ‘‘double bubble’’ sign. Initial radiographic reports detailing duodenal atresia described gaseous distention of the stomach and duodenum with an ‘‘hourglass’’ appearance [1], with later reports refining the description of duodenal obstruction to include the now classic ‘‘double bubble’’ moniker [2]. The larger gastric bubble occupies the left upper quadrant, with a smaller duodenal bubble in the right upper quadrant or right mid abdomen (Figs. 1, 2). The dilation reflects postnatal gas swallowing, with the atretic duodenal segment not allowing distal passage of swallowed gas. Antenatal diagnosis is now possible with ultrasound or fetal MRI, both of which depict a fluid-filled dilated stomach and duodenum [3]. Emesis within the first 24 hours of life raises concern for duodenal obstruction. The emesis of duodenal atresia is frequently bilious, as the atretic site is often distal to the Ampulla of Vater. Nonbilious emesis, similar to that seen in hypertrophic pyloric stenosis, may occur if the atretic site is proximal to the Ampulla [4].

The String of Pearls Sign.

Often referred to as the ‘‘Queen of Gems’’, pearls have been revered spanning both time and culture [1] (Fig. 1). The String of Pearls Sign metaphorically describes a radiographic finding highly suggestive of mechanical small bowel obstruction. As small bowel becomes distended intraluminal fluid traps gas along the valvulae conniventes. Upright radiographs depict a row of elliptical lucencies produced by the meniscal surface of fluid on one side and the bowel wall on the other, evocative of a string of pearls [2–4] (Fig. 2A). The imaging sign can also be observed at computed tomography [5] (Fig. 2B).

The “Sausage” pancreas

IgG4-related disease (IgG4RD) is a complex, immunemediated illness characterized by lymphoplasmacytic infiltration of multiple organs, accompanied by an elevated serum IgG level [1]. Pancreatic involvement has been termed autoimmune pancreatitis (AIP) [2]. On contrast-enhanced CT (CECT), the pancreas is enlarged, with featureless border and effacement of the lobular contour (the ‘‘sausage’’ analogy as shown in Fig. 1). A capsule-like rim, thought to represent inflammatory cell infiltrate, encircles the pancreas with a halo of amorphous soft tissue attenuation material [3]. The dense lymphoplasmacytic infiltrate can afflict extrapancreatic tissues as well, including kidneys (Fig. 2), retroperitoneum, bile ducts, and salivary glands [3].

The small bowel feces sign

Diagnosing SBO on plain films can be difficult, especially if the bowel is fluid filled. In contrast, the sensitivity of diagnosing SBO with CT approaches 100% [1]. The small bowel feces sign is a CT manifestation of small bowel obstruction: particulate material mixed with gas bubbles in the small bowel, similar to the appearance of stool in the colon [2] (Figs. 1, 2). This altered appearance presumably reflects stasis and resultant absorption of more fluid than normal in the small bowel. It usually occurs proximal to the site of obstruction, thus helpful in locating a transition point in some cases [3, 4]. The sign has a positive predictive value of 82% [2] and has been reported in approximately 7–8% of cases of small bowel obstruction [5].