- Email: [email protected]
The functional consequences of colectomy
The Functional Consequences of Colectomy Hastings K. Wright, MD, New Haven, Connecticut
tract with water, sodium, or digestible food. Everything ingested is absorbed, with excess water and electrolytes then being excreted in the urine. (Unfortunately, excess calories remain on board.) Equally important, the intact healthy intestine almost totally conserves water, sodium, and nutrients under a variety of conditions of zero intake. (Table I.) This intestinal capacity to conserve, when combined with known renal conservation mechanisms, is clearly important in the long-term survival of starving man. In contrast, it is obvious to both patients and surgeons alike that resection of the entire colon or that part of it distal to the midtransverse colon produces an entirely different picture even if the entire small intestine is left healthy and intact. An ileostomy never stops running, and a proximal colostomy cannot be kept continent on a normal diet. This clinical reality is most unfortunate. Yet, the incontinence from such stomas obscures the fact that almost 90 per cent of all fluid and electrolytes ingested into or secreted into the upper intestinal tract has already been absorbed before the terminal ileum is reached, and probably more than 95 per cent before the midtransverse colon. Obviously, the care of patients with ostomies could be improved immeasurably and the continual threat of extracellular fluid volume depletion removed from their lives if water absorption could be improved only minimally in the absence of the colon. The remainder of this report describes the current understanding of this problem in our laboratory.
One rigidly enforced rule on the surgical metabolic ward at the University Hospitals of Cleveland in the 1950’s was that all excreta from balance study patients be collected and chemically analyzed. While directors William Holden and William Abbott obviously wished to miss no clue in their studies of surgical nutrition, the laborious process of analyzing everything appeared to be largely unnecessary to the junior research associates. Only the analyses of urine seemed to be of any import, for only these analyses demonstrated predicted variations in excretion rates of water, electrolyte, and solute as Doctors Holden and Abbott changed the experimental conditions. In contrast to the urine results, the fecal analyses were a drab, monotonous, indecipherable lot, never changing no matter how extreme the conditions of gastrointestinal deprivation or overload became. (Indeed, rectal excretion was so minimal in these studies that the medical illustrator constantly complained to me that the insignificant fecal losses could not be charted legibly on the same graphs used to portray oral intake and urinary losses.) The value of these fecal analysis data were not apparent to me until more than a decade later, after Doctor Abbott’s premature death and Doctor Holden’s diversion to other scientific challenges. At that time as we began to study patients with the short gut syndrome or other major losses of intestine, we re-reviewed the data in the laboratory notebooks of that era for baseline material. The lessons of those experiments were immediately apparent, for they showed clear evidence that it is impossible to overload an intact, normal intestinal
Water Absorptive
From the Department of Surgery, Yale University School of Medicine and the Yale-New Haven Medical Center, New Haven, Connecticut. This work was supported in part by USPHS Grant #AM-17362-01. Reprint requests should be addressed to Hastings K. Wright, MD. Department of Surgery, Yale University School of Medicine, Yale-New Haven Medical Center, New Haven, Connecticut 06504.
One way to measure the water absorptive capacity of the intact normal colon is to pass a tube down through the ileocecal valve and then perfuse the colon with a solution similar to that found in normal ileostomy fluid. When such an experiment was done by Levitan et al [I], the intact colon
532
Capacity
of the Intact Colon
The American Journal of Surgery
Colectomy
proved capable of absorbing up to 2.5 L of water and 400 to 600 mEq of sodium per day, a volume three or four times the daily amount measured in our laboratory from normal, mature ileostomies in patients on regular diets [2]. The same authors also found that almost half the absorptive capacity of the colon lies in its first third, proximal to the site of most transverse colostomies. This finding has not yet been thoroughly appreciated by surgeons who operate on the terminal ileum and right colon. Thus, the intact colon has considerable reserve capacity, which may be called into play only when small bowel absorption becomes deficient (for example, during acute infectious enteritis or after massive small bowel resection) or when intake becomes massive (as in some of the experiments of Doctors Abbott and Holden). A second way to estimate large bowel absorptive capacity is to study patients who lack this organ. A striking difference from normal fecal excretion is immediately apparent. Unlike the normal patient, the patient with an ileostomy excretes water and electrolytes in direct proportion to his intake and at rates seven to ten times greater than the normal patient on the same normal diet. Although these losses by the patient with an ileostomy do not approach normal water and sodium. intake, they do obligate the patient to almost daily ingestion of salt and water to avoid extracellular fluid volume depletion and make him very susceptible to the formation of renal stones. Furthermore, and in contrast with normal patients, output by the ileostomy does not cease when intake ceases; patients with an ileostomy studied in our laboratory on zero intake for three or more days had not less than 300 to 400 ml of output by the ileostomy containing 25 to 30 mEq of sodium. (Table II.) Such unreplaced continued losses would produce significant extracellular fluid volume depletion within a week despite maximal renal conservation of water and sodium. In contrast, patients with intact colon can live for several weeks on less than 5 mEq per day of sodium intake. An additional difference between normal patients and patients with an ileostomy is noted when sodium intake is increased significantly greater than normal limits. No increase in fecal output is noted in the normal patient, but the patient with an ileostomy is forced to increase his water excretion in direct proportion to sodium intake [3,4]. If water ingestion does not increase commensurately, oliguria and hyponatremia develop in the patient with an ileostomy.
Volume 130, November 1975
TABLE
I
Conservation
by the Intact
Intestinal
Tract*
Experimental Condition
Stool Water per Day (ml)
House diet, 3 meals per
less than 150
less than 5
less than 50
less than 150
less than 5
less than 50
less than 150
less than 5
less than 50
less than 150
less than 5
less than 50
day No oral intake for 22 hours 6.000 calorie, high protein, high fat diet 300 mEq sodium diet
Stool Sodium Stool Calories per Day per Day (mEq)
* Unpublished data from the laboratory notebooks of experiments by Doctor William Holden and Doctor William Abbott in 1956.
TABLE
II
Conservation an lleostomy
Experimental Condition Normal
diet, 3
meals per day No oral intake for 72 hours 300 mEq so-
by the Patient
I leostomy Water per Day (ml)
with lleostomy Sodium per Day(mEd
750 to 1,000
80 to 120
300 to 400
25 to 30
2,000
to 3,000
200 to 250
dium diet
Thus, the contrast between the response of patients with ileostomies and normal patients to starvation and to excessive solute intake dramatically demonstrates the true absorptive function of the colon. Adaptatlon by the Small Intestine In the Absence of the Colon Effluents from a recently constructed ileostomy may exceed 2,000 ml per day, an abnormal rate of loss that is at least partly attributable to partial obstruction due to postoperative edema. However, this rate of loss is soon reduced by half as the ileostomy matures, and it decreases even more in succeeding weeks on the same normal diet. Direct intubation studies of patients with an ileostomy suggest strongly that this further reduction is due to adaptation of the ileum to increase both water and sodium absorption per unit length in the absence of the colon [2]. Direct intubation studies of patients with intact colon supports this view, since volume flow through the ileum is higher in patients with intact colon than in patients with an ileostomy [5]. Furthermore, the distal ileal mucosa undergoes definite hypertrophy in patients with
533
an ileostomy, a change that might be expected to accompany increased transport capacity. An additional interesting clinical phenomenon well known to surgeons and their patients for many years is the ability of patients with ileorectal anastomosis to gradually develop quite acceptable bowel activity in the complete absence of the colon [6]. Studies in both man and the rat in our laboratory show that the mere addition of the rectum to the end of the terminal ileum reduces water loss by one half or more and sodium loss by two thirds or more compared with patients with an ileostomy on similar diets. The increased absorptive capacity that makes this possible is located in the terminal ileum rather than the rectum in the rat [7], but the exact site of increased absorption has not been completely determined in man. However, the evidence to date suggests that the rectum, which normally absorbs isotonic fluid only very slowly, probably plays no direct absorptive role in the increased absorptive capacity of patients who underwent ileorectostomy. It may act as a valve at the end of the ileum to slow transit and promote more efficient water and sodium transport from the adapted ileum. Such a role for the rectum has already been demonstrated in volumogenic diarrhea in patients with intact colon, a process not dissimilar to the diarrhea of salt-loaded patients with an ileostomy [S]. The possibility that adapted ileal mucosa can assume absorptive function found only in the intact colon of man is further suggested by our recent studies of patients with continent ileostomies. We have found that an ileostomy with a,valve [9] occasionally can produce an almost solid effluent despite the fact that the only mucosa available for this activity is the same ileal mucosa proximal to a standard ileostomy. Not all continent ileostomies do this, and the reason is not clear. Bacterial overgrowth may be one reason, and partial obstruction may also decrease absorptive capacity in some of those pouches. Phillips [IO] has also found that some continent ileostomies can produce an effluent with a sodium concentration similar to that found in the normal rectum. These findings suggest that human ileal mucosa has the capacity to absorb sodium and water to a much greater degree than previously thought possible [3]. In the future, it may be possible to combine this capacity with dietary manipulation and further technical improvements in construction of an ileostomy to considerably improve the patient’s condition. However, much remains to
534
be learned, particularly in the area of the physical or chemical process in normal man that converts the fecal stream to solid stool. While water content certainly determines stool volume, its percentage concentration in normal stool and in diarrhea1 stool is almost the same, suggesting that an unknown mechanism in addition to bowel absorptive capacity is partly responsible for fecal consistency. Summary The colon plays a decisive role in salt and water conservation in the intact human, normally removing from the terminal intestine approximately one liter of isotonic fluid that escapes small bowel absorption. The primary purpose of this colon function is probably to prevent extracellular fluid volume depletion and only incidentally to produce a normal solid stool. The patient with an ileostomy can partly adapt to replace the absorptive capacity lost after colectomy but is still vulnerable if salt and water intake ceases completely. In contrast, patients with ileorectostomies and some patients with continent ileostomies can almost totally adapt to loss of the colon. These findings suggest that the ileal mucosa can adapt under certain conditions to absorb at rates and concentrations previously thought impossible. This property of ileal mucosa might be utilized in the future to significantly improve the condition of patients who require total colectomy. References 1. Levitan Ft. Fordtran JS, Burrows BA, et al: Water and salt absorption in the human colon. J C/in invest 41: 1754, 1962. 2. Wright HK, Cleveland JC, Tilson MD, et al: Morphology and absorptive capacity of the ileum after ileostomy in man. Am J Surg 117: 242, 1969. 3. Wright HK, Tilson MD: ii method for testing the functional significance of tight ileostomy stomas. Am J Surg 123: 417, 1972. 4. Kramer P: The effect of varying sodium loads on the ileal excreta of human iieostomized subjects. J C/in invest 45: 1710,1966. 5. Giller J. Phillips SF: Colohic absorption of electrolytes and water in man: a comparison of 24-hour ileal content and feces. Grisfroenferology 58: 95 1, 1970. 6. Lillehei RC, Wangensteen OH: Bowel function after colectomy for cancer, polyps, and diverticulitis. JAMA 150: 163, 1955. 7. Wright HK, Poskitt BS, Cleveland JC, et al: The effect of total colectomy on morphology and absorptive capacity of ileum in the rat. J Surg Res 9: 301, 1969. 8. Grantham RN, Brecher GA, Jacobson ED: Fluid dynamics in voluinogenic diarrhea. D@sfion 3: 1, 1970. 9. Kock NG: lleostomy without external appliances. Ann Surg 173: 545, 1971. 10. Phillips SF: Personal communication.
Tha
American
Journal
of Surgery
tract with water, sodium, or digestible food. Everything ingested is absorbed, with excess water and electrolytes then being excreted in the urine. (Unfortunately, excess calories remain on board.) Equally important, the intact healthy intestine almost totally conserves water, sodium, and nutrients under a variety of conditions of zero intake. (Table I.) This intestinal capacity to conserve, when combined with known renal conservation mechanisms, is clearly important in the long-term survival of starving man. In contrast, it is obvious to both patients and surgeons alike that resection of the entire colon or that part of it distal to the midtransverse colon produces an entirely different picture even if the entire small intestine is left healthy and intact. An ileostomy never stops running, and a proximal colostomy cannot be kept continent on a normal diet. This clinical reality is most unfortunate. Yet, the incontinence from such stomas obscures the fact that almost 90 per cent of all fluid and electrolytes ingested into or secreted into the upper intestinal tract has already been absorbed before the terminal ileum is reached, and probably more than 95 per cent before the midtransverse colon. Obviously, the care of patients with ostomies could be improved immeasurably and the continual threat of extracellular fluid volume depletion removed from their lives if water absorption could be improved only minimally in the absence of the colon. The remainder of this report describes the current understanding of this problem in our laboratory.
One rigidly enforced rule on the surgical metabolic ward at the University Hospitals of Cleveland in the 1950’s was that all excreta from balance study patients be collected and chemically analyzed. While directors William Holden and William Abbott obviously wished to miss no clue in their studies of surgical nutrition, the laborious process of analyzing everything appeared to be largely unnecessary to the junior research associates. Only the analyses of urine seemed to be of any import, for only these analyses demonstrated predicted variations in excretion rates of water, electrolyte, and solute as Doctors Holden and Abbott changed the experimental conditions. In contrast to the urine results, the fecal analyses were a drab, monotonous, indecipherable lot, never changing no matter how extreme the conditions of gastrointestinal deprivation or overload became. (Indeed, rectal excretion was so minimal in these studies that the medical illustrator constantly complained to me that the insignificant fecal losses could not be charted legibly on the same graphs used to portray oral intake and urinary losses.) The value of these fecal analysis data were not apparent to me until more than a decade later, after Doctor Abbott’s premature death and Doctor Holden’s diversion to other scientific challenges. At that time as we began to study patients with the short gut syndrome or other major losses of intestine, we re-reviewed the data in the laboratory notebooks of that era for baseline material. The lessons of those experiments were immediately apparent, for they showed clear evidence that it is impossible to overload an intact, normal intestinal
Water Absorptive
From the Department of Surgery, Yale University School of Medicine and the Yale-New Haven Medical Center, New Haven, Connecticut. This work was supported in part by USPHS Grant #AM-17362-01. Reprint requests should be addressed to Hastings K. Wright, MD. Department of Surgery, Yale University School of Medicine, Yale-New Haven Medical Center, New Haven, Connecticut 06504.
One way to measure the water absorptive capacity of the intact normal colon is to pass a tube down through the ileocecal valve and then perfuse the colon with a solution similar to that found in normal ileostomy fluid. When such an experiment was done by Levitan et al [I], the intact colon
532
Capacity
of the Intact Colon
The American Journal of Surgery
Colectomy
proved capable of absorbing up to 2.5 L of water and 400 to 600 mEq of sodium per day, a volume three or four times the daily amount measured in our laboratory from normal, mature ileostomies in patients on regular diets [2]. The same authors also found that almost half the absorptive capacity of the colon lies in its first third, proximal to the site of most transverse colostomies. This finding has not yet been thoroughly appreciated by surgeons who operate on the terminal ileum and right colon. Thus, the intact colon has considerable reserve capacity, which may be called into play only when small bowel absorption becomes deficient (for example, during acute infectious enteritis or after massive small bowel resection) or when intake becomes massive (as in some of the experiments of Doctors Abbott and Holden). A second way to estimate large bowel absorptive capacity is to study patients who lack this organ. A striking difference from normal fecal excretion is immediately apparent. Unlike the normal patient, the patient with an ileostomy excretes water and electrolytes in direct proportion to his intake and at rates seven to ten times greater than the normal patient on the same normal diet. Although these losses by the patient with an ileostomy do not approach normal water and sodium. intake, they do obligate the patient to almost daily ingestion of salt and water to avoid extracellular fluid volume depletion and make him very susceptible to the formation of renal stones. Furthermore, and in contrast with normal patients, output by the ileostomy does not cease when intake ceases; patients with an ileostomy studied in our laboratory on zero intake for three or more days had not less than 300 to 400 ml of output by the ileostomy containing 25 to 30 mEq of sodium. (Table II.) Such unreplaced continued losses would produce significant extracellular fluid volume depletion within a week despite maximal renal conservation of water and sodium. In contrast, patients with intact colon can live for several weeks on less than 5 mEq per day of sodium intake. An additional difference between normal patients and patients with an ileostomy is noted when sodium intake is increased significantly greater than normal limits. No increase in fecal output is noted in the normal patient, but the patient with an ileostomy is forced to increase his water excretion in direct proportion to sodium intake [3,4]. If water ingestion does not increase commensurately, oliguria and hyponatremia develop in the patient with an ileostomy.
Volume 130, November 1975
TABLE
I
Conservation
by the Intact
Intestinal
Tract*
Experimental Condition
Stool Water per Day (ml)
House diet, 3 meals per
less than 150
less than 5
less than 50
less than 150
less than 5
less than 50
less than 150
less than 5
less than 50
less than 150
less than 5
less than 50
day No oral intake for 22 hours 6.000 calorie, high protein, high fat diet 300 mEq sodium diet
Stool Sodium Stool Calories per Day per Day (mEq)
* Unpublished data from the laboratory notebooks of experiments by Doctor William Holden and Doctor William Abbott in 1956.
TABLE
II
Conservation an lleostomy
Experimental Condition Normal
diet, 3
meals per day No oral intake for 72 hours 300 mEq so-
by the Patient
I leostomy Water per Day (ml)
with lleostomy Sodium per Day(mEd
750 to 1,000
80 to 120
300 to 400
25 to 30
2,000
to 3,000
200 to 250
dium diet
Thus, the contrast between the response of patients with ileostomies and normal patients to starvation and to excessive solute intake dramatically demonstrates the true absorptive function of the colon. Adaptatlon by the Small Intestine In the Absence of the Colon Effluents from a recently constructed ileostomy may exceed 2,000 ml per day, an abnormal rate of loss that is at least partly attributable to partial obstruction due to postoperative edema. However, this rate of loss is soon reduced by half as the ileostomy matures, and it decreases even more in succeeding weeks on the same normal diet. Direct intubation studies of patients with an ileostomy suggest strongly that this further reduction is due to adaptation of the ileum to increase both water and sodium absorption per unit length in the absence of the colon [2]. Direct intubation studies of patients with intact colon supports this view, since volume flow through the ileum is higher in patients with intact colon than in patients with an ileostomy [5]. Furthermore, the distal ileal mucosa undergoes definite hypertrophy in patients with
533
an ileostomy, a change that might be expected to accompany increased transport capacity. An additional interesting clinical phenomenon well known to surgeons and their patients for many years is the ability of patients with ileorectal anastomosis to gradually develop quite acceptable bowel activity in the complete absence of the colon [6]. Studies in both man and the rat in our laboratory show that the mere addition of the rectum to the end of the terminal ileum reduces water loss by one half or more and sodium loss by two thirds or more compared with patients with an ileostomy on similar diets. The increased absorptive capacity that makes this possible is located in the terminal ileum rather than the rectum in the rat [7], but the exact site of increased absorption has not been completely determined in man. However, the evidence to date suggests that the rectum, which normally absorbs isotonic fluid only very slowly, probably plays no direct absorptive role in the increased absorptive capacity of patients who underwent ileorectostomy. It may act as a valve at the end of the ileum to slow transit and promote more efficient water and sodium transport from the adapted ileum. Such a role for the rectum has already been demonstrated in volumogenic diarrhea in patients with intact colon, a process not dissimilar to the diarrhea of salt-loaded patients with an ileostomy [S]. The possibility that adapted ileal mucosa can assume absorptive function found only in the intact colon of man is further suggested by our recent studies of patients with continent ileostomies. We have found that an ileostomy with a,valve [9] occasionally can produce an almost solid effluent despite the fact that the only mucosa available for this activity is the same ileal mucosa proximal to a standard ileostomy. Not all continent ileostomies do this, and the reason is not clear. Bacterial overgrowth may be one reason, and partial obstruction may also decrease absorptive capacity in some of those pouches. Phillips [IO] has also found that some continent ileostomies can produce an effluent with a sodium concentration similar to that found in the normal rectum. These findings suggest that human ileal mucosa has the capacity to absorb sodium and water to a much greater degree than previously thought possible [3]. In the future, it may be possible to combine this capacity with dietary manipulation and further technical improvements in construction of an ileostomy to considerably improve the patient’s condition. However, much remains to
534
be learned, particularly in the area of the physical or chemical process in normal man that converts the fecal stream to solid stool. While water content certainly determines stool volume, its percentage concentration in normal stool and in diarrhea1 stool is almost the same, suggesting that an unknown mechanism in addition to bowel absorptive capacity is partly responsible for fecal consistency. Summary The colon plays a decisive role in salt and water conservation in the intact human, normally removing from the terminal intestine approximately one liter of isotonic fluid that escapes small bowel absorption. The primary purpose of this colon function is probably to prevent extracellular fluid volume depletion and only incidentally to produce a normal solid stool. The patient with an ileostomy can partly adapt to replace the absorptive capacity lost after colectomy but is still vulnerable if salt and water intake ceases completely. In contrast, patients with ileorectostomies and some patients with continent ileostomies can almost totally adapt to loss of the colon. These findings suggest that the ileal mucosa can adapt under certain conditions to absorb at rates and concentrations previously thought impossible. This property of ileal mucosa might be utilized in the future to significantly improve the condition of patients who require total colectomy. References 1. Levitan Ft. Fordtran JS, Burrows BA, et al: Water and salt absorption in the human colon. J C/in invest 41: 1754, 1962. 2. Wright HK, Cleveland JC, Tilson MD, et al: Morphology and absorptive capacity of the ileum after ileostomy in man. Am J Surg 117: 242, 1969. 3. Wright HK, Tilson MD: ii method for testing the functional significance of tight ileostomy stomas. Am J Surg 123: 417, 1972. 4. Kramer P: The effect of varying sodium loads on the ileal excreta of human iieostomized subjects. J C/in invest 45: 1710,1966. 5. Giller J. Phillips SF: Colohic absorption of electrolytes and water in man: a comparison of 24-hour ileal content and feces. Grisfroenferology 58: 95 1, 1970. 6. Lillehei RC, Wangensteen OH: Bowel function after colectomy for cancer, polyps, and diverticulitis. JAMA 150: 163, 1955. 7. Wright HK, Poskitt BS, Cleveland JC, et al: The effect of total colectomy on morphology and absorptive capacity of ileum in the rat. J Surg Res 9: 301, 1969. 8. Grantham RN, Brecher GA, Jacobson ED: Fluid dynamics in voluinogenic diarrhea. D@sfion 3: 1, 1970. 9. Kock NG: lleostomy without external appliances. Ann Surg 173: 545, 1971. 10. Phillips SF: Personal communication.
Tha
American
Journal
of Surgery