Intestines

Published on 02/03/2015 by admin

Filed under Basic Science

Last modified 02/03/2015

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 1002 times

Chapter 33 Intestines

Diarrhoea

A patient complaining of ‘diarrhoea’ may in fact describe a wide variety of colorectal symptoms. The World Health Organization defines diarrhoea as the passage of three or more loose or liquid stools per day (or more frequent liquid passage than is normal for the individual). Diarrhoea ranges from a mild and socially inconvenient symptom to a major cause of death and malnutrition in the developing world. The first priority of therapy is to preserve fluid and electrolyte balance.

Mechanism of diarrhoea

Fluid and electrolyte treatment

Infectious diarrhoea

This includes travellers’ diarrhoea, where up to half of the diarrhoea that afflicts visitors to tropical and subtropical countries is associated with enterotoxigenic strains of Escherichia coli; other bacteria including Shigella and Salmonella spp., viruses including the Norwalk family, and parasites (particularly Giardia lamblia) have also been implicated.

Transmission is almost invariably by ingestion of contaminated food and water, which indicates the most effective way of reducing risk.

Infectious diarrhoea as a rule is self-limiting and oral rehydration is generally all that is required. Antimotility agents are relatively contraindicated due to concerns of reduced pathogen clearance and toxic megacolon but may be permissible in mild cases. The use of antibiotics is controversial as even in cases of bacterial dysentery they do not reduce duration of symptoms by more than 48 hours, and there is hard in vitro as well as anecdotal evidence that their use in patients with certain bacterial infections (e.g. E. coli O175) can precipitate haemolytic-uraemic syndrome (HUS), which can be life-threatening. Antibiotics may be indicated if the patient is toxic or immunosuppressed, or if invasive infections (e.g. Shigella) are suspected or confirmed. Many regimens are used (commonly ciprofloxacin) but macrolides are theoretically less prone to precipitating HUS in susceptible patients.

Chemotherapy is available for certain specific organisms if enteric infection is confirmed on stool culture, e.g. amoebiasis, giardiasis (see Index).

Diarrhoea due to Clostridium difficile (‘C. diff’)

C. diff infection may range from an offensive but limited diarrhoeal illness to a life-threatening toxic pseudomembranous colitis, and for this reason occupies such a prominent place in the public consciousness. The major risk factors for infection are older age, significant co-morbidites, recent antibiotic use and a history of recent (within 3 months) hospitalisation. Virtually all antibiotics have been implicated as a risk factor for C. diff infection (including, rarely, metronidazole, one of the mainstays of treatment), but clindamycin, quinolones, cephalosporins and other β-lactams are particularly notorious.

First-line treatment has traditionally consisted of 7–14 days of metronidazole by mouth. There is better evidence for a prolonged (4-week) tapering course of oral vancomycin, although this tends to be reserved for severe, refractory or relapsed infections. The tapering course allows the killing of reactivated spores which may have survived initial treatment. Vancomycin not absorbed from the GI tract is excreted renally; it must therefore be given orally (125 mg four times daily initially; occasionally doubled) and monitoring of serum levels is unnecessary.

There are also some data supporting the use of more novel treatments, although solid evidence is lacking. Probiotics and faecal enemas (prepared using normal faeces from unaffected donors), for example, are thought to work by recolonising the bowel with non-pathogenic bacterial flora, whereas intravenous immunoglobulin probably works by neutralising pathogenic toxins.

Secretory diarrhoea due to vasoactive peptides

Octreotide, a synthetic somatostatin analogue (see p. 549), inhibits the release of peptides that mediate certain alimentary secretions, and may be used to relieve diarrhoea due to neuroendocrine tumours such as carcinoids and VIPomas (tumours that produce VIP).

Constipation

Constipation means different things to different people, and is difficult to define formally. Generally it refers to infrequent, hard to pass bowel motions. Rome III criteria2define constipation as 2 + of the following over 12 weeks: < 3 stools per week, straining > 1/4 of the time, passage of hard stools, incomplete evacuation, sensation of anorectal blockage.

There are multiple causes of constipation which should be excluded or treated. Symptomatic treatment involves the use of laxatives, which are medicines that promote defaecation, largely by reducing the viscosity of the contents of the lower colon. They are classified as follows:

Stool bulking agents