Villous adenoma of the colon. Study of a patient with severe fluid and electrolyte disturbances

Gastric villous adenoma: a case report and review of the literature

BACKGROUND

Villous adenoma is the one subtype of adenomatous polyp that is very uncommon in the stomach. Data regarding clinical characteristics, natural history, and prognosis were scarce.

CASE PRESENTATION

This report presented an 87-year-old Thai woman with a large gastric villous adenoma incidentally revealed in a computed tomography of chest for the evaluation of right pleural effusion. The esophagogastroduodenoscopy demonstrated a huge, glossy, proliferative polypoid mass involving gastric cardia, fundus, and a lesser curve of the upper body. The pathological report confirmed villous adenoma with low grade dysplasia. Although surgical resection was suggested, the patient denied any treatment due to advanced age and multiple comorbidities. She was generally well after 12 months of clinical and radiologic surveillance.

CONCLUSION

From literature review, only 14 cases of gastric villous adenoma were reported to date. Most of the lesions were large and symptomatic. Malignancy presented in 43% of the cases. Nevertheless, our patient remained asymptomatic without surgical removal following a 12-month period.

The patient with metabolic alkalosis

Metabolic alkalosis defined by the increase of both plasma HCO3- level (>26 mmol/L) and blood arterial pH (>7.43) is quite frequent and usually accompanied by hypokalemia. Its pathogenesis requires both the generation of alkalosis and its maintenance. Generation may be due to excessive hydrogen ion loss by the gastrointestinal tract (e.g. vomiting) or by the kidney (e.g. use of loop diuretics) or may be due to exogenous base gain. Maintenance reflects the inability of the kidney to excrete the excess of bicarbonate because of hypovolemia, chloride depletion, hypokalemia, hyperaldosteronism, renal failure or a combination of these factors. The evaluation of volemic status and measurement of urinary Cl- and plasma levels of renin and aldosterone are crucial to identify the cause(s) of metabolic alkalosis. The cornerstone of treatment is the correction of existing depletions and the prevention of further losses. In vomiting-induced chloride depletion alkalosis, infusion of potassium chloride restores the excretion of bicarbonate by the kidney.

The McKittrick-Wheelock syndrome: a case of acute renal failure due to neoplastic cholera

The McKittrick-Wheelock syndrome is characterized by severe electrolyte and fluid depletion as a result of rectal tumor hypersecretion. Typically, a metabolic acidosis ensues. We report the case of a 58-year-old man who presented with a mixed metabolic acidosis and alkalosis. He was hyponatremic, hypokalemic, and hypochloremic, with acute renal failure on blood testing. Following fluid resuscitation, a predominant alkalemia was observed. The patient was found to be passing 1.5 L of mucous per rectum per day, containing high concentrations of sodium and potassium, similar to that observed in cholera stool. A large rectal villous adenoma was discovered on sigmoidoscopy, and definitive management was achieved by removal of the tumor. This case provides a demonstration of the ranging metabolic disturbance associated with secretory diarrhea. Other endogenous and infective causes are discussed, and mechanisms compared with the case described.

Acid-base disturbances in gastrointestinal disease

Disruption of normal gastrointestinal function as a result of infection, hereditary or acquired diseases, or complications of surgical procedures uncovers its important role in acid-base homeostasis. Metabolic acidosis or alkalosis may occur, depending on the nature and volume of the unregulated losses that occur. Investigation into the specific pathophysiology of gastrointestinal disorders has provided important new insights into the normal physiology of ion transport along the gut and has also provided new avenues for treatment. This review provides a brief overview of normal ion transport along the gut and then discusses the pathophysiology and treatment of the metabolic acid-base disorders that occur when normal gut function is disrupted.

Pathophysiology of potassium absorption and secretion by the human intestine

When normal people ingest 90 mEq/day of K+ in their diet, they absorb about 90% of intake (81 mEq) and excrete an equivalent amount of K+ in the urine. Normal fecal K+ excretion averages about 9 mEq/day. The vast majority of intestinal K+ absorption occurs in the small intestine; the contribution of the normal colon to net K+ absorption and secretion is trivial. K+ is absorbed or secreted mainly by passive mechanisms; the rectum and perhaps the sigmoid colon have the capacity to actively secrete K+, but the quantitative and physiological significance of this active secretion is uncertain. Hyperaldosteronism increases fecal K+ excretion by about 3 mEq/day in people with otherwise normal intestinal tracts. Cation exchange resin by mouth can increase fecal K+ excretion to 40 mEq/day. The absorptive mechanisms of K+ are not disturbed by diarrhea per se, but fecal K+ losses are increased in diarrheal diseases by unabsorbed anions (which obligate K+), by electrochemical gradients secondary to active chloride secretion, and probably by secondary hyperaldosteronism. In diarrhea, total body K+ can be reduced by two mechanisms: loss of muscle mass because of malnutrition and reduced net absorption of K+; only the latter causes hypokalemia. Balance studies in patients with diarrhea are exceedingly rare, but available data emphasize an important role for dietary K+ intake, renal K+ excretion, and fecal K+ losses in determining whether or not a patient develops hypokalemia. The paradoxical negative K+ balance induced by ureterosigmoid anastomosis is described. The concept that fecal K+ excretion is markedly elevated in patients with uremia as an intestinal adaptation to prevent hyperkalemia is analyzed; we conclude that the data do not convincingly show the existence of a major intestinal adaptive response to chronic renal failure.

Acid-base disturbances in gastrointestinal disease

Gastrointestinal disorders are associated with severe and often complex acid-base disturbances. We review the most important types of metabolic alkalosis and metabolic acidosis associated with gastrointestinal disorders, excluding liver disease. Special emphasis is placed on pathophysiologic mechanisms. This information may help the clinician understand the generation and maintenance of these disorders and to plan an effective therapeutic approach.

Villous papilloma of the rectum (with unusual complications)

A case is reported in which a villous papilloma of the rectum was complicated by severe electrolyte losses and acute renal failure. Successful management by peritoneal dialysis and early surgery is described.