ABSORPTION AND SECRETION IN THE LARGE INTESTINE

Hydration by colonic enteroclysis: An alternative to parenteral hydration in patients with high-output double enterostomy

BACKGROUND

High-output double enterostomies (DESs) result in sodium and fluid loss responsible for frequent episodes of dehydration and hospitalizations. Hydration by enteroclysis (HE) is an alternative to parenteral hydration when the small bowel, or the downstream colon, is accessible and functional.

METHODS

A retrospective analysis was conducted on all consecutive patients admitted in our institution with high-output (≥1200 ml per 24 h) DES and access to downstream intestine (including colon), who were treated by enteroclysis between 2015 and 2019. A sodium chloride and bicarbonate solution was instilled through a tube inserted in the colon. The objectives were diuresis >1 L, natriuresis >40 mmol/24 h, and urinary sodium-to-potassium ratio >1.

RESULTS

HE was conducted in 52 patients (24 female, 28 male). Initially, 30 patients received intravenous support. Fifteen patients (50%) were weaned from all parenteral support, of whom 11 of 12 (92%) received fluid and electrolyte support and 4 of 18 (22%) received parenteral nutrition (PN). When intravenous fluids were still required, daily volumes decreased from 2714 ± 1424 to 1578 ± 1000 ml per 24 h (P = .001), as did the energetic intake (NS), from 1439 ± 556 to 1230 ± 362 kcal per 24 h (P = .096).

CONCLUSION

HE through the efferent intestine limits the requirement for parenteral hydration in patients with high-output DES. For patients with intestinal failure dependent on PN, it reduces daily infused volumes.

Constitutive modeling of the passive inflation-extension behavior of the swine colon

In the present work, we propose the first structural constitutive model of the passive mechanical behavior of the swine colon that is validated against physiological inflation-extension tests, and accounts for residual strains. Sections from the spiral colon and the descending colon were considered to investigate potential regional variability. We found that the proposed constitutive model accurately captures the passive inflation-extension behavior of both regions of the swine colon (coefficient of determination R²=0.94±0.02). The model revealed that the circumferential muscle layer does not provide significant mechanical support under passive conditions and the circumferential load is actually carried by the submucosa layer. The stress analysis permitted by the model showed that the colon tissue can distend up to 30% radially without significant increase in the wall stresses suggesting a highly compliant behavior of the tissue. This is in-line with the requirement for the tissue to easily accommodate variable quantities of fecal matter. The analysis also showed that the descending colon is significantly more compliant than the spiral colon, which is relevant to the storage function of the descending colon. Histological analysis showed that the swine colon possesses a four-layer structure similar to the human colon, where the longitudinal muscle layer is organized into bands called taeniae, a typical feature of the human colon. The model and the estimated parameters can be used in a Finite Element framework to conduct simulations with realistic geometry of the swine colon. The resulting computational model will provide a foundation for virtual assessment of safe and effective devices for the treatment of colonic diseases.

Influence of sodium chloride on the beta-glucuronidase activity of Clostridium perfringens and Escherichia coli

While the beta-glucuronidase activity of intact cells of Clostridium perfringens was higher in 0.95% sodium chloride (NaCl) than that in 0, 0.1 or 0.5%, that of Escherichia coli was higher in 0.1% NaCl than that in 0, 0.5 or 0.95% NaCl in 0.1 mol l-1 KH2PO4. However, the enzyme activity of both species of intact cells was higher in buffer containing 16 mEq sodium, 134 mEq potassium and 16 mEq chloride per litre than in that containing 146 mEq sodium, 13 mEq potassium and 146 mEq chloride. These findings suggest that bacterial cells are affected by the presence of NaCl and that the effect of NaCl on the activity of bacterial beta-glucuronidase may differ by location in the large intestine.

Electrolyte disorders in the elderly

Normal human ageing impairs homeostatic mechanisms in such a way as to exaggerate and prolong the effects of stress. Thus, an event--pathological or traumatic--which produces a trivial change in plasma electrolytes of young people may produce major oscillations of plasma levels in the elderly, which take much longer to return to 'normal levels'. This is especially apparent with perturbations in the plasma levels of sodium and potassium, mainly due to changes in renal function and neurohumeral mechanisms which occur with increasing age. Paradoxically this does not mean that the clinician should be over-enthusiastic in attempting to correct electrolyte imbalance because, for the same reasons, the danger of over-treatment producing the opposite and equally dangerous electrolyte imbalance is ever-present. Indeed, in clinical practice most electrolyte disturbances in old age are iatrogenic in origin. Cautious patience and vigilance should be the clinical approach with elderly patients. A high index of suspicion should lead to a careful appraisal of the drug (diuretic, intravenous fluid) and environmental (dehydration) aetiology of most electrolyte disturbances in old age.

Urease as a contributing factor in ulcerative lesions of the colon

Urease immunization protects animals against the development of uremic colitis. This indicates that ammonia formed by bacterial urease is the causative factor in the breakdown of the colonic mucosa.

In vitro effects of gastrin on the movement of electrolytes across the human colon

Using an in vitro system, the effect of gastrin on the colonic handling of water and electrolytes has been investigated. Gastrin converted the normal mucosal absorption of water and sodium into a net secretion. The colonic response to gastrin was done-related with respect to sodium, and the effects were greater when it was added to the serosal side. The potassium handling of the isolated colonic mucosa was not altered by gastrin. At a concentration of 800pg/ml, gastrin signficantly reduced the normal movement of sodium from mucosa to serosa (absorption) but significantly increased serosal to mucosal movement (secretion). This alteration in the bidirectional flux of ions under the influence of gastrin may be clinically important and could account in partt for the diarrhoea associated with the Zollinger-Ellison syndrome.

Further experience with peritoneo-venous shunt for ascites

A specially devised pressure-sensitive valve forms the basis for a new peritoneo-venous shunt operation which delivers ascitic fluid continuously into the venous system. It is effective in ascites attributed to different causes. The procedure is simple and brings a long lasting relief with recovery in strength and nutrition and improved kidney function. Hepatorenal syndrome in ascites is reversed.

Intestinal absorption of water and electrolytes

1. Recent advances in knowledge of intestinal physiology have provided some insight into disturbed mechanisms and their clinical effects; for example, diarrhoea can now be defined biochemically as excessive fluid and electrolyte loss due to their malabsorption or excessive secretion. 2. Because of differences in structure and in absorptive and secretory mechanisms, the various parts of the gut perform different functions. In the jejunum, transport activity is extensive and the rapid equilibration of its content provides the optimal absorptive mixture. Functionally, the ileum and colon are similar; compared with the jejunum, they have greater absorptive capacity for electrolytes and generate significantly higher transmural electrical potentials. In the colon, some transport mechanisms are potentiated by adrenocortical steroids. 3. Water and electrolyte absorption and secretion are the end-products of bidirectional fluxes across the intestinal wall that are several times greater than net movement in either direction. Secretion is the surplus of negative flux (into the lumen) and absorption the surplus of positive flux (out of it). 4. Many electrolyte transport mechanisms require the absorption of other electrolytes or non-electrolytes, and some are concerned with electrolyte exchange. Water transport is always passive, in the direction of solute flow, but its solvent drag can move solutes across the intestinal membrane.

Colonic and small intestinal response to intravenous prostaglandin F2 alpha and E2 in man

The effects of intravenous infusions of prostaglandins (PGs) F2 alpha(0-4 or 0-8 mug kg-1 min-1) or E2 (0-08 or 0-1 mug kg-1 min equals1) on net colonic movement of water and electrolytes and on ileal flow were measured in eight healthy males by simultaneous ileal and colonic perfusion. Ileal flow was increased by PGF2 alpha (six subjects) from a mean of 1-69 ml min-1 to 4-63 ml min-1 (P smaller than 0-01); it also increased in the two subjects given PGE2. Colonic absorptive function was not significantly diminished by either prostaglandin. These results suggest that diarrhoea due to prostaglandins originates in the small intestine.

Pancreatic islet cell tumour with watery diarrhoea and hypokalaemia

A further patient with watery diarrhoea and hypokalaemia in association with a non-beta islet cell tumour of the pancreas is reported. The mechanism by which fluid and electrolyte losses are produced is discussed and cases previously reported are reviewed.

Measurement of electrical potentials of the human rectum and pelvic colon in normal and aldosterone-treated patients

A method is described which allows rapid measurement of the electrical potential difference across colonic mucosal epithelium to be carried out during routine sigmoidoscopy. The potential differences measured had a mean value of 25 mV (range 4 to 51 mV) in 27 subjects with normal bowel. Six hours after two intravenous injections of 0.5 mg aldosterone the potential difference had risen to 60 mV (range 37 to 101 mV). The time course of responses studied after a single injection of aldosterone showed that the potential allowance rose within four hours and had fallen again after 18 hours. Urinary sodium concentrations and sodium/potassium ratios fell after aldosterone injections, the time course of the changes being similar to that of the potential differences of the colon. Sodium concentration of stool fluid also fell. The concentration of chloride in the stool fluid was consistent with a passive distribution of chloride according to the electrochemical gradient, but that of potassium was considerably greater than expected from a passive distribution, suggesting that potassium is actively secreted into the lumen of the colon.

Syndromes of water and electrolyte depletion of intestinal origin

Because of the important part played by the intestine in maintaining the constancy of the internal environment, any disturbance in the orderly sequence of secretion and reabsorption of water and electrolytes can quickly lead to severe fluid depletion. Malabsorption of water and electrolytes may occur in diseases of the intestinal mucosa or following massive resection of bowel or as a result of disordered intestinal motility. The handling of fluids by the bowel may be altered by the action of hormones or of bacterial toxins, or in the presence of neoplasms. Electrolyte disorders may result from the introduction of abnormal solutions into the intestinal lumen.

Management of the clinical problems requires a clear understanding of the abnormal mechanisms and urgent attention to the re-institution of water and salt balance, restoration of acid-base status and replacement of lost potassium.