CHAPTER 33
Anorectal diseases

Adil E. Bharucha¹ and Arnold Wald²

¹ Mayo Clinic College of Medicine, Rochester, MN, USA

² University of Wisconsin‐Madison, Madison, WI, USA

This chapter provides a visual review of anorectal anatomy, functions, and pathologies. We begin with a coronal section of the anorectum, which highlights the orientation of the anal sphincters and pelvic floor muscles (Figure 33.1). Common instruments for anorectal examinations more frequently used by a colorectal surgeon than a gastroenterologist are shown in Figure 33.2. The equipment used for rigid proctosigmoidoscopy is shown in Figure 33.2a. Because symptomatic internal hemorrhoids are one of the most common lesions seen by the practicing gastroenterologist, we have elected to show a photograph of the simplest, most widely used instrument for management of internal hemorrhoids, the Barron‐type rubber band ligator with its ancillary equipment (see Figure 33.2c).

Hemorrhoids are the most common anal lesions seen in practice; therefore, pictures of external and different degrees of internal hemorrhoids are critical to any atlas on anal disorders (Figures 33.4–33.8). Hemorrhoids may be treated using a variety of nonsurgical techniques. One modality is banding using a ligator device attached to the tip of an endoscope (Figure 33.9). Examples of an anorectal abscess, the classification of anorectal fistulas, rectal prolapse, solitary rectal ulcer, and chronic anal fissure are shown in Figures 33.10–33.14. These important lesions are all best diagnosed by means of simple inspection. Figures 33.15 and 33.16 depict normal anorectal and pelvic floor motion during defecation and when subjects squeeze (i.e., contract) their pelvic floor muscles. Figures 33.17–33.27 illustrate the techniques for digital rectal examination and encapsulate the pathophysiology of fecal incontinence. Anorectal manometry discloses a variety of disturbances in fecal incontinence (Table 33.1). Figures 33.28–33.30 summarize the cardinal clinical features of syndromes associated with functional anorectal pain.

Finally, we show examples of carcinoma of the anus (Figures 33.31 and 33.32). One fairly subtle lesion is Bowen disease (cutaneous squamous cell carcinoma in situ), which may be confused with the anal lesions of dermatitis and psoriasis.