Hydrocolonic ultrasonography: Should still waters run deep?

GASTROENTEROLOGY 1995;109:1014-1019

SELECTED SUMMARIES Henry J. Binder, M.D. Selected Summaries Editor

Yale University School of Medicine New Haven, Connecticut 08520-8019 STAFF OF CONTRIBUTORS Hannah Carey, Madison, Wl Grace H. Elta, Ann Arbor, MI Greg Fitz, Durham, NC Vivek V. Gumaste, Elmherst, NY Lynn Hornsby-Lewis, Dallas, TX Cyrus Kapadia, New Haven, CT

Ronald L. Koretz, Sylmar, CA William M. Lee, Dallas, TX Thomas A. Miller, Houston, TX Ravinder K. Mittal, Charlottesville, VA Pankaj Jay Pasricha, Baltimore, MD Anil K. Rustgl, Boston, MA

Mitchell L. Schubert, Richmond, VA Konrad Schulze-Deirieu, Iowa City, IA Fergus Shanahan, Wilton, Cork, Ireland Joseph G. Sweeting, New York, NY Richard C. Thirlby, Seattle, WA Jacques Van Dam, Boston, MA

HYDROCOLONIC ULTRASONOGRAPHY: SHOULD STILL WATERS RUN DEEP?

phy is less useful than colonoscopy for detecting colorectal polyps and cancers and questioned its use as a screening test.

Chui DW, GoodingAW, McQuaidKR, GriswoldV, GrendellJH

Comment. Hydrocolonic ultrasonography, the instillation of water into the colon during conventional transabdominal uhrasonography, has been proposed as a sensitive and less invasive method to image the colon (N Engl J Med 1992;327:65-69; Lancet 1990;335:144146). To properly assess the study by Chui et al., it should be compared with that of Limberg, who previously reported on the clinical applications of hydrocolonic ultrasonography. Limberg used hydrocolonic ultrasonography to examine patients with inflammatory bowel disease and suggested that this new imaging technique could differentiate patients with Crohn's disease from those with ulcerative colitis by virtue of its ability to provide highly detailed images of the colonic wall (Am J Gastroenterol 1994;89:1051-1057). Limberg used hydrocolonic ultrasonography to diagnose and stage colonic tumors and showed that the instillation of water into the colon improved the diagnostic yield of conventional ultrasonography (N Engl J Med 1992;327:65-69). In his study, Limberg prospectively examined 300 patients using hydrocolonic ultrasonography before colonoscopy. The colon was shown ultrasonographically from the rectosigmoid transition to the cecum in 97% of patients studied. Hydrocolonic ultrasonography detected 28 of 29 cancers (sensitivity, 97%), 38 of 42 polyps >7 mm in diameter (sensitivity, 91%), and 3 of 12 polyps < 7 mm in diameter (sensitivity, 25%). In addition to providing images of the colonic lumen, hydrocolonic uhrasonography permitted detailed examination of the mural architecture of the colonic wall and surrounding connective tissue, thus providing a more precise staging for colonic tumors. The author suggested that hydrocolonic ultrasonography could facilitate the diagnosis and staging of colonic tumors. He also suggested that this new imaging technique "would be a suitable screening procedure for colonic carcinoma because of its sensitivity, its cost-effectiveness, its availability and suitability for use as an outpatient procedure, its safety, and its acceptance by patients" (Lancet 1990;335:144-146). Chui et al. conducted their study to evaluate the use of hydrocolonic ultrasonography as a new imaging modality for detecting colonic polyps and tumors. Their results are in sharp contrast to the earlier published reports noted above. In their study, Chui et al. were unable to identify any of the four colonic cancers subsequently detected by colonoscopy. In addition, the sensitivity for detecting large (>7 mm diameter) polyps was poor. What is the reason for the wide variation in the reported results of these two studies? There are several possible explanations for the different outcomes of these two studies. First, as noted by Chui et al., obese patients

(University of California and Veterans Affairs Medical Center, San Francisco, California). Hydrocolonic ultrasonography in the detection of colonic polyps and tumors. N Engl J Med 1994;331:1685-1688. Chui et al. evaluated the sensitivity of hydrocolonic ultrasonography for detecting colonic polyps and tumors and compared the results with colonoscopy. The investigators studied 52 patients (50 men and 2 women) referred for colonoscopy for a positive screening test for fecal occult blood (n = 24), iron-deficiency anemia (n = 6), hematochezia (n = 14), and other indications for colonoscopy (n = 8). Patients were prepared for colonic examination by limiting their diet to clear liquids and ingesting 4 L of an electrolyte solution (Colyte; Reed and Carrick, Jersey City, NJ) on the day before the procedure was performed. One to 2 L water was instilled into the colon immediately before the procedure was performed. Beginning at the time of water instillation, continuous transabdominal colonic ultrasonography was performed by board-certified radiologists experienced in diagnostic ultrasonography. Colonoscopy was performed immediately after hydrocolonic ultrasonography and reached the cecum in each patient. Endoscopists performing colonoscopy were unaware of the results of the preceding hydrocolonic ultrasonography. Colonoscopic examination established that 26 patients had polyps (n = 66), 3 patients had cancer and polyps, and 1 patient had cancer and no polyps. Hydrocolonic ultrasonography did not detect any of the cancers (sensitivity, 0) but did detect one polyp > 7 m m in diameter (sensitivity, 12.5%) and one polyp < 7 m m in diameter (sensitivity, 6.9%). HydrocoIonic ultrasonography suggested the presence of five masses and polyps not confirmed by colonoscopy (false-positive rate, 19.2%). Six patients were unable to complete the hydrocolonic ultrasonography procedure because of discomfort or inability to retain water. One patient sustained two vasovagal episodes, causing the procedure to be terminated prematurely. The authors of this study concluded that hydrocolonic ultrasonogra-

September 1995

SELECTED SUMMARIES 1015

present an obstacle to good ultrasonographic imaging using 5.0- or 7.0-MHz ultrasound transducers. Because a lower frequency ultrasound transducer was required to visualize the colon in obese patients (3.5 MHz), the image resolution and therefore the ability to distinguish between fecal material from neoplasia became poor. In one obese patient (weight, 145 kg), none of the 17 polyps detected at colonoscopy were visualized using hydrocolonic ultrasonography. More than 30% of patients studied by Chui et al. weighed more than 90 kg. Another possible explanation for the different results of hydrocoIonic ultrasonography imaging between these two reports may be the skill of the operator. Although the ultrasonographers who performed the procedure in the study by Chui et al. "were board-certified radiologists with extensive experience in all aspects of ultrasonography, including endoscopic, transrectal, transvaginal, and vascular techniques," their study was conducted on a relatively limited number of patients (n = 52). The prior study by Limberg reported the results of 300 patients evaluated using this technique (N Engl J Med 1992; 327:65-69). In addition, studies reported by the same investigator in other patient populations, e.g., reports of hydrocolonic ultrasonography in patients with inflammatory bowel disease (Am J Gastroenterol 1994;89:1051-1057), and previous reports of studies in patients with colorectal neoplasia (Lancet 1990;335:144-146) suggest that the operator in the prior study was more experienced in the procedure. However, before a new technology may be considered for widespread use, its success must be proven in many hands and by many operators of varying experience. In both studies, the rectum presented a relative "blind area" for imaging using hydrocolonic ultrasonography because of the position of the overlying urinary bladder and bony pelvis. Therefore, to completely examine the colon and rectum would require two procedures (e.g., hydrocolonic ultrasonography and flexible sigmoidoscopy). The arguments against this approach to evaluating the colon are similar to those made for the combination of barium-contrast radiography and flexible sigmoidoscopy. How shall we evaluate hydrocolonic ultrasonography? Is this new method for imaging the colon all wet? Are we being flooded with new imaging techniques? Are we drowning in a sea of controversy? Undoubtedly, hydrocolonic ultrasonography is less expensive than colonoscopy. It is also less invasive and does not require conscious sedation and may therefore be expected to be associated with less risk when compared with colonoscopy. However, as noted by Chui et al., hydrocolonic ultrasonography is also less sensitive than colonoscopy for detecting colonic neoplasia. Colonoscopy provides the gastroenterologist the opportunity to perform endoscopic biopsy, which may provide a tissue diagnosis in the case of a suspected malignancy. More importantly, colonoscopy permits the endoscopic resection of malignant or premalignant polyps, which has been shown to confer a benefit to the patient with respect to the subsequent development and consequences of colorectal cancer (N Engl J Med 1993;329: 1977-1981). Therefore, as noted by Chui et al., hydrocolonic ultrasonography in its present form is limited as a screening procedure for colorectal neoplasia and will require substantial refinement before it assumes a role in the imaging armamentarium for colonic disease. SCOTT TENNER, M.D., M.P.H. JACQUES VAN DAM, M.D., Ph.D.

Reply. In our experience with predominantly overweight patients, hydrocolonic sonography is ineffective as a screening test for colon cancer. A lower frequency sonography transducer was required to

visualize the colon, and the image resolution was poor. Adherent stool was difficult to discriminate from actual lesions despite changes in transducer pressure and patient position. We agree with Tenner and Van Dam that before hydrocolonic sonography can be considered for general practice, "its success must be proven in many hands and by many operators of varying experience." Our study showed that previous high sensitivity and specificity rate of diagnosing colonic neoplasm by Dr. Limberg cannot be reproduced and used in general practice. In conclusion, the use of hydrocolonic sonography in screening colon cancer in general practice is limited. Hydrocolonic sonography may be useful in selected groups of patients with thin body habitus or a pediatric population. Substantial training experience is required before general practice. DAVID W. CHUI, M.D. GRETCHEN A. W. GOODING, M.D. KENNETH R. McQUAID, M.D.

FAMILY HISTORY INCREASES THE RISK OF COLORECTAL CANCER Fuchs CS, Giovanucci EL, Colditz GA, Hunter DJ, Speizer FE, Willett WC (Channing Laboratory Department of Medicine, Brigham and W o m e n ' s Hospital and Harvard Medical School, Boston; Division of Medical Oncology, Dana-Farber Cancer Institute, Boston; and Department of Epidemiology, Environmental Health and Nutrition, Harvard School of Public Health, Boston, Massachusetts). A prospective study of family history and the risk of colorectal cancer. N Engl J Med 1994; 331 : 1 6 6 9 - 1 6 7 4 (December 22, 1994). The potential influence of heredity on colorectal cancer incidence has become a topic of major interest. Many retrospective studies have noted a relationship between a positive family history and an increased risk of colorectal cancer development. These investigators attempt to quantify that risk by using information obtained in two large prospective cohort studies: the Nurses' Health Study and the Health Professionals Followup Study. Both of these ongoing studies consist of questions sent to participants at baseline and are then followed up every 2 years. The Nurses' Health Studies began with 121,700 registered female nurses in 1976. The Health Professionals Followup Study began with 51,269 men in various health-related fields in 1986. Both studies asked questions on known or suspected risk factors for cancer and coronary artery disease along with an assessment of diet. The women were asked about colorectal cancer in first-degree relatives in 1982 and again in 1988. The men were asked about colorectal cancer in their parents in 1986. In 1990, they were asked about all first-degree relatives. The reported cases of colorectal cancer in family members were not verified in the study. Participants were also asked about smoking, age, weight, height, activity level, use of aspirin, and any previous colonoscopy or sigmoidoscopy. A 61-item food frequency questionnaire was sent to the women in 1980, and a 131-item questionnaire was sent to the men in 1986. Participants were