Rigid rectosigmoidoscopy has largely been replaced by the flexible sigmoidoscope for routine elective screening and diagnostic workups. The rigid rectosigmoidoscope is superior to the flexible sigmoidoscope in measuring distances accurately, examining an unprepared patient, and when trying to work within the bowel lumen, for example when removing foreign bodies. The larger lumen of the rigid rectosigmoidoscope allows for a larger biopsy of lesions where pathology is in question. The cost associated with this examination is less than that for flexible sigmoidoscopy. The rigid rectosigmoidoscope can be purchased in a disposable model that performs well. It is important for a physician who evaluates and treats problems related to the colon, rectum, and anus to be familiar with rigid rectosigmoidoscopy.
The significant anatomy of the anal canal that is necessary to understand and to perform rigid rectosigmoidoscopy is covered in Chapter 70 describing the anatomy for anoscopy (Figures 70-1 & 70-2). The gross anatomy of the colon is reviewed in Figure 71-1A. It is important to be aware of the large folds that impinge on the lumen of the colon called the valves of Houston (Figure 71-1B). These folds must be gently flattened to advance the rigid rectosigmoidoscope and clearly see the proximal side of the valve when looking for pathology. It is also necessary to understand the three-dimensional path followed by the distal colon, rectum, and anus. The direction to follow will be toward the patient's umbilicus for 3 to 5 cm initially. The anus then turns posteriorly as it becomes the rectum and follows the curve of the sacrum. The rectosigmoid junction is reached at 10 to 15 cm, at which point the lumen sharply angulates anteriorly and to the left. Because the scope is rigid and straight, it is necessary to angle the tip of the rigid rectosigmoidoscope toward the lumen of the bowel and then gently flatten the haustra or move the patient's colon so that the lumen is in a straight line.
Anatomy of the colon. A. The gross anatomy. B. Cross-section through the colon demonstrating the valves of Houston.
Many of the indications for rigid rectosigmoidoscopy are the same as those for performing flexible sigmoidoscopy. The rigid scope is more useful when the bowel is not properly prepared, if a bigger biopsy is needed, or if a larger instrument needs to be passed to the last 25 cm. The following is a list of such indications.
The rigid rectosigmoidoscope may be used to evaluate the rectum and sigmoid colon in the office or the Emergency Department. Rectal bleeding can be evaluated in the unprepared patient. It is particularly helpful to determine if stool is mixed with blood when evaluating hematochezia and determining if colonoscopy is indicated. Foreign bodies in the rectum or sigmoid colon can be removed. The rigid rectosigmoidoscope will allow ...