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Sapir Medical Center 44281 Kfar Saba, Israel
I read with great interest the original report by Dr. Pickhardt et al. [1] about the imaging findings in the abdominal compartment syndrome. This entity is indeed not widely recognized among radiologists because it is usually diagnosed clinically. One of the features that was reported to characterize this syndrome is the positive round belly sign, measured as an increased ratio of anteroposterior-to-transverse (AP-T) abdominal diameter. By comparing this ratio in the four reported patients with the abdominal compartment syndrome to the ratio calculated from 100 consecutive nonemergent CT abdominal scans, Pickhardt et al. reported a cutoff value of 0.80 with 100% sensitivity and 94% specificity. Using a value of 0.82 increased the specificity to 99%; however, as stated by Pickhardt et al., "further investigation is necessary before any conclusions can be made regarding the clinical usefulness of this measurement." I responded to this challenge by measuring the AP-T abdominal diameter ratio in 77 abdominal CT scans of adults with significant peritoneal and retroperitoneal disease from teaching file cases that I have collected in my own practice. None had clinical signs of abdominal compartment syndrome. The ratio was based on the same measurements that were shown in the drawing by Pickhardt et al. The maximal anteroposterior and transverse abdominal diameters were taken at the level where the left renal vein crosses the aorta, not including the subcutaneous fat [1].
There were 15 patients (11 men and 4 women; age range, 18-82 years; mean, 39 years) with blunt abdominal trauma who underwent CT at admission. The mean AP-T abdominal diameter ratio was 0.68 (range, 0.57-0.78). Eighteen patients (10 women and 8 men; age range, 37-88 years; mean, 58 years) suffered from moderate to severe acute pancreatitis. None underwent surgery before the CT study. The mean AP-T abdominal diameter ratio in this group was 0.73 (range, 0.6-0.82). Three of the 18 patients had a ratio equal to or greater than 0.80.
A third group included 44 patients (24 women and 20 men; age range, 37-86 years; mean, 62 years) with various peritoneal diseases, such as malignant peritoneal disease, primary or secondary tuberculous peritonitis, pseudomembranous colitis, and liver cirrhosis, and patients with small-bowel obstruction. In this group, the mean AP-T abdominal diameter ratio was 0.74 (range, 0.6-0.94). Eleven of the 44 patients (25%) had a ratio equal or greater to 0.80. None of the 14 patients with a ratio equal or greater to 0.8 had compression of the inferior vena cava.
In conclusion, radiologists should be familiar with the clinical presentation and imaging features of abdominal compartment syndrome. The pathogenesis of this syndrome is the acute pathologic elevation of the intraabdominal pressure. However, in my opinion (based on the limited data I've described) the round belly sign cannot be relied on as a specific imaging finding for this entity. As known from daily practice, any severe abdominal disease may cause significant abdominal distention.
References
Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis, MO 63110
My colleagues and I welcome the letter from Dr. Zissin regarding our recent paper [1] The primary motivation for our work was to familiarize radiologists with the abdominal compartment syndrome, which is a life-threatening condition resulting from acute elevation of intraabdominal pressure that requires emergent surgical decompression [1,2,3]. Pertinent CT findings seen in our small series included tense retroperitoneal infiltration, compression of the inferior vena cava, mass effect on the kidneys, diffuse bowel-wall thickening, and bilateral inguinal herniation.
Prominent rounding of the abdomen, analogous to the gross physical appearance of massive abdominal distention, was an additional observation that we reported. In slightly more quantitative terms, the ratio of the anteroposterior-to-transverse abdominal diameter appeared increased, a finding we termed the "round belly sign" when the diameter was greater than 0.80. In fact, the ratio was 0.83 or greater in all four patients with proven abdominal compartment syndrome in our series (we arbitrarily chose to round the cutoff value to 0.80 because it seemed less awkward). By comparison, only one out of 100 consecutive CT scans performed in a nonemergent setting had a ratio greater than 0.82 (99% specific). However, given the preliminary nature of our data, we were justifiably hesitant to advocate implementation of this ratio and I applaud the efforts of Dr. Zissin to address our admonition that "further investigation is necessary before any conclusions can be made regarding the clinical usefulness of this measurement."
Dr. Zissin astutely applied our abdominal ratio to a more deserving control group that consisted of patients with "significant peritoneal and retroperitoneal disease." Not surprisingly, the specificity of the round belly sign decreased with this group of 77 patients, falling to 82%. I would point out that Dr. Zissin considered a ratio equal to 0.80 as positive, whereas we did not. Furthermore, it would be an interesting, albeit academic, pursuit to see how much the specificity would increase in Dr. Zissin's series if the more precise cutoff value (>0.82) were applied; all false-positives in the second group and likely some from the third group of patients would be excluded.
With these light protestations aside, I agree with Dr. Zissin that one should not feel compelled to suggest the abdominal compartment syndrome solely on the basis of a positive round belly sign on CT, especially in a stable patient. Clearly, recognition and integration of all relevant CT findings in the appropriate clinical setting should prevail over reliance on any contrived measurement when confronted with this life-threatening condition. In patients who develop the abdominal compartment syndrome, the rounded appearance of the abdomen on CT merely reflects the underlying pathology, which is much more critical to appreciate—namely, tense retroperitoneal and peritoneal infiltration by varying combinations of blood, fluid, and edematous tissue. Early recognition of the acute increase in intraabdominal pressure and prompt decompression can be lifesaving in this setting.
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  G. Laffargue, P. Taourel, M. Saguintaah, and A. Lesnik CT Diagnosis of Abdominal Compartment Syndrome Am. J. Roentgenol., March 1, 2002; 178(3): 771 - 772. [Full Text] [PDF]
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