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Detailed knowledge of clinical anatomy is an indispensable prerequisite for the diagnosis and therapy of coloproctological diseases. Therefore this chapter presents the essential aspects of the anatomy of the colon, rectum, anal canal, and pelvic floor that are relevant for coloproctologists. Anatomy is described for the different colonic segments, rectal ampulla, upper and lower anal canal, corpus cavernosum recti, proctodeal glands, anal sphincter complex, and pelvic floor muscles. The anatomic structures mediating anal continence are highlighted. Special emphasis is given to topographical aspects and anatomic landmarks relevant for surgical approaches. Access routes to both autonomic and somatic nerves, as well as blood supply and lymphatic drainage, are addressed for each anatomic compartment. In particular, the topography of perirectal fasciae and spaces and their relationship to pelvic autonomic nerves are described in detail to meet the criteria for nerve-sparing total mesorectal excision. Finally, the anatomical peculiarities of the pelvic floor levels (subperitoneal, ischioanal, and perianal spaces) are presented and set in a clinical context.

The main functions of the colon and rectum are transport and storage of feces, absorption of water and electrolytes, and absorption of short-chain fatty acids. The colon and rectum have specific contraction patterns that are mainly controlled by the enteric nervous system. Furthermore, colorectal contractions are modulated by the sympathetic and parasympathetic nervous systems, several hormones, and the immune system. The physiology of the colon and rectum undergoes diurnal and postprandial changes.

Anal continence depends on complicated interactions between the internal and external anal sphincters, the puborectalis muscle, rectal compliance, anorectal sensibility, anorectal reflexes, and colorectal motility.

Defecation is usually initiated by colonic mass movements. Stretching of the rectal wall stimulates rectal contractions through the defecation reflex and relaxation of the internal anal sphincters through the rectoanal inhibitory reflex. Defecation is facilitated by relaxation of the puborectalis muscle and enforced by a Valsalva maneuver.

Hemorrhoidal disease is one of the most common benign disorders of the lower gastrointestinal tract. Treatment options comprise conservative as well as surgical therapy and are still applied arbitrarily in accordance with the surgeon’s expertise. The aim of this chapter is therefore to assess a stage-dependent approach for treatment of hemorrhoidal disease in order to derive evidence-based recommendations for a clinical routine. The most common treatment methods are discussed with respect to hemorrhoidal disease in extraordinary conditions such as inflammatory bowel disease and recurrent hemorrhoids. Tailored hemorrhoidectomy is preferable for individualized treatment with regard to the shortcomings of the traditional Goligher classification in segmental or circular hemorrhoidal prolapse.

An anal fissure is a tear in the epithelial lining of the anal canal, distal to the dentate line. It is accompanied by a significant increase in the tone of the internal anal sphincter. Anal pain is usually intense, occurs during or minutes after a bowel movement, and can last from minutes to hours. It may be accompanied by minimal bleeding. A fissure is usually located in the posterior (in 90 % of cases) or anterior midline (in 10 % of women and 1–5 % of men with anal fissure). If there are multiple fissures or occur at a lateral position, other anal pathologies must be ruled out (e.g., tuberculosis, syphilis, HIV, Crohn’s disease). Treatment of anal fissure is based on general measures and pharmacological intervention. General measures consist of sitz baths, avoiding the presence of hard stools by using laxatives or significantly increasing fiber intake, and using analgesics. Pharmacological treatment is based on three groups: a nitric oxide donor (glyceryl trinitrate), calcium channel antagonists (diltiazem, nifedipine), and botulinum toxin. The results of these treatments are better than placebo but inferior to surgery. If these treatments fail, surgery is the best option. Sphincterotomy is an outpatient procedure with a success rate greater than 90 %, but it has a postoperative incontinence rate between 3 % and 15 %. A chance of postoperative incontinence is the main reason why drug treatment is now considered as the first therapeutic option, especially in patients with a high risk for incontinence.

Fistula in ano is a common condition mostly caused by inflammation of the proctodeal anal glands. This results in an acute anal abscess or chronic fistula. Anal fistulas are classified according to their relation to the anal sphincter muscles: subcutaneous, subanodermal, intersphincteric, transsphincteric, suprasphincteric or extrasphincteric. Distal fistulas including negligible amounts of sphincter muscle are treated by a lay-open technique (fistulotomy, fistulectomy), whereas proximal fistulas are cured using sphincter-saving procedures (advancement flap, fistulectomy with primary sphincter reconstruction, ligation of intersphincteric fistula tract, fistula plugs, fistula clip). The best surgical method balances the chance of healing and the risk of incontinence. An experienced colorectal surgeon also plays an important role.

Perianal skin conditions are common. They are best managed by a proctologist in conjunction with a dermatologist. This brief review covers common perianal skin conditions and suggests management options in an evidence-based manner. Perianal dermatitis is the most common perianal skin condition. Up to one-third of patients with perianal dermatitis have a relevant contact allergy. It is recommended that all patients with this condition undergo cutaneous allergy testing. Dietary manipulation as part of management does not seem to have any evidence base, unless skin maceration is thought to be to the result of diarrhea, in which case stool thickeners may be of some benefit. Lower bowel endoscopy is important in perianal dermatitis to assess for internal hemorrhoids or neoplastic disease as a possible contributory factor. Perianal infections, especially those with the human papillomavirus, are also discussed in this chapter.

Several surgical techniques for dealing with pilonidal disease (PD) exist. Primary closure allows for quicker healing. Off-midline closure provides for better healing rates compared with midline closure. Fewer recurrences occur with open healing compared with midline closure. Systematic reviews of each method are prone to bias. Many minor small variations in technique occur, adding to the great divergence of published results and in the understanding of the pathogenesis of PD. The literature suggests a trend away from wide excision and healing by secondary intention toward less invasive procedures. Flap techniques may be used for complicated recurrent PD. The Limberg flap is widely used and provides satisfactory results.

Fecal incontinence is not a rare condition; it is an often unvoiced disorder. Approximately 2 % of the general population is affected, and it is more frequent with increased age. Various classifications are used to reflect the severity of symptoms and their impact on quality of life. Diagnostic management leading to therapeutic interventions depends on disease stage; in the majority of patients diagnostic techniques are simple and therapy is conservative, following a pragmatic approach. Diagnostics may help to distinguish functional from morphological causes and thus direct treatment. Operative therapy is indicated if conservative treatment fails to adequately relieve symptoms. Interventions range from minimally invasive outpatient procedures to more extended surgery with sphincter replacement. The mainstays of surgery for fecal incontinence are sphincter repair and sacral nerve stimulation. Although the indications for the various surgical procedures can overlap, there are distinct conceptual differences. In addition, practitioners are increasingly coming to appreciate that, for some patients, only a combination of various therapeutic modes will improve symptoms.

Although constipation is no longer treated primarily with surgery, surgeons continue to regularly see patients with constipation in ward and ambulatory settings. It is therefore critical to have a practical approach with respect to diagnosis, investigation, and management. Further, recent pharmacological and surgical advances are giving new hope to some patients with disabling chronic symptoms. This chapter gives an overview of constipation in general and then focuses on the more surgically relevant problem of chronic constipation. The chapter deliberately excludes a detailed discussion of defecation disorders (covered in Chap. 11), although this distinction is actually relevant only when specific surgery is considered.

Defecation disorders refers to the inability to efficiently and rapidly empty the rectum of its contents on demand. Functional and anatomic abnormalities coexist to give combined symptoms of 'obstructed defecation' a source of discomfort and impaired quality of life. These symptoms include abnormal anal function (anismus), perineal descent, rectocele and enterocele, rectal intussusception, and overt prolapse. Management is based on a detailed assessment of the terminal bowel anatomy and function to identify a cause. Medical treatment and pelvic floor retraining are first-line treatment. Various types of surgical approaches currently designed to correct anatomic abnormalities in order to improve function can be carried out in selected patients. In this difficult area of functional pelvic floor disorders, a multidisciplinary approach as developed in “pelvic floor clinics” is a useful adjunct to the traditional colorectal approach. Providing information to the patient and his/her relatives is essential, especially when surgery is considered.