Enteric hyperoxaluria secondary to small bowel resection: use of computer simulation to characterize urinary risk factors for stone formation and assess potential treatment protocols

Kidney stones are common in patients with short-bowel syndrome receiving long-term parenteral nutrition: A predictive model for urolithiasis

BACKGROUND

In short-bowel syndrome (SBS) treated with parenteral nutrition (PN), multiple complications can occur. The etiology of kidney stones may be linked to the underlying disease thrombosis, surgical complications, complications of therapy for cancer, Crohn's disease, metabolic abnormalities resulting from morphological and functional changes in the gastrointestinal tract, and to treatment used. We analyzed all these parameters in a large cohort of patients receiving home PN (HPN), to define the incidence of stones and groups of patients particularly at risk of stone formation. One of the objectiveswas to develop a predictive model of urolithiasis.

METHODS

This observational retrospective study included 459 patients with SBS recieving HPN in a single center. Patient records were evaluated for demographics, SBS etiology, and underlying disease, anatomy of the gastrointestinal tract, intestinal failure classification, nutrition regimen, and presence of urolithiasis.

RESULTS

Kidney stones were diagnosed in 24% of patients. Nodifferences in incidence were noted between the various etiologic groups. The incidence in patients with a colon in continuity and those with an end stoma was similar. The length of residual small bowel did not play a role in stone formation. There were no differences between patients according to the severity of intestinal failure. In patients treated with PN and limited oral feeding, the risk of urolithiasis was twice as high as in patients receiving PN only.

CONCLUSIONS

Patients developed urolithiasis with no relation to the SBS etiology. The risk of kidney stone formation was higher in patients recieving PN with oral feeding.

Subsequent urinary stone events are predicted by the magnitude of urinary oxalate excretion in enteric hyperoxaluria

 

Data directly demonstrating the relationship between urinary oxalate (UOx) excretion and stone events in those with enteric hyperoxaluria (EH) are limited. Therefore, we assessed the relationship between UOx excretion and risk of kidney stone events in a retrospective population-based EH cohort. In all, 297 patients from Olmsted County, Minnesota were identified with EH based upon having a 24-h UOx ≥40 mg/24 h preceded by a diagnosis or procedure associated with malabsorption. Diagnostic codes and urologic procedures consistent with kidney stones during follow-up after baseline UOx were considered a new stone event. Logistic regression and accelerated failure time modeling were performed as a function of UOx excretion to predict the probability of new stone event and the annual rate of stone events, respectively, with adjustment for urine calcium and citrate. Mean ± standard deviation age was 51.4 ± 11.4 years and 68% were female. Median (interquartile range) UOx was 55.4 (46.6-73.0) mg/24 h and 81 patients had one or more stone event during a median follow-up time of 4.9 (2.8-7.8) years. Higher UOx was associated with a higher probability of developing a stone event (P < 0.01) and predicted an increased annual risk of kidney stones (P = 0.001). Estimates derived from these analyses suggest that a 20% decrease in UOx is associated with 25% reduction in the annual odds of a future stone event. Thus, these data demonstrate an association between baseline UOx and stone events in EH patients and highlight the potential benefit of strategies to reduce UOx in this patient group.

BACKGROUND

Data directly demonstrating the relationship between urinary oxalate (UOx) excretion and stone events in those with enteric hyperoxaluria (EH) are limited.

METHODS

We assessed the relationship between UOx excretion and risk of kidney stone events in a retrospective population-based EH cohort. In all, 297 patients from Olmsted County, Minnesota were identified with EH based upon having a 24-h UOx ≥40 mg/24 h preceded by a diagnosis or procedure associated with malabsorption. Diagnostic codes and urologic procedures consistent with kidney stones during follow-up after baseline UOx were considered a new stone event. Logistic regression and accelerated failure time modeling were performed as a function of UOx excretion to predict the probability of new stone event and the annual rate of stone events, respectively, with adjustment for urine calcium and citrate.

RESULTS

Mean ± SD age was 51.4 ± 11.4 years and 68% were female. Median (interquartile range) UOx was 55.4 (46.6-73.0) mg/24 h and 81 patients had ≥1 stone event during a median follow-up time of 4.9 (2.8-7.8) years. Higher UOx was associated with a higher probability of developing a stone event (P < 0.01) and predicted an increased annual risk of kidney stones (P = 0.001). Estimates derived from these analyses suggest that a 20% decrease in UOx is associated with 25% reduction in the annual odds of a future stone event.

CONCLUSIONS

These data demonstrate an association between baseline UOx and stone events in EH patients and highlight the potential benefit of strategies to reduce UOx in this patient group.

[Stone therapy-use and limitations of the guidelines]

Increase of medical knowledge, technical innovation together with a demographic change, and increase of stone incidence in daily practice challenges guideline preparation and clinical studies. Increasing interdisciplinary collaboration in stone treatment can also be demonstrated in the number of affiliated professional and working groups in the current guideline update. The following case illustrates treatment options in a symptomatic patient harbouring bilateral stones and metabolic risk factors. Decision guidance for treatment and recurrence prevention measures are presented on the basis of expert opinion and available published evidence.

Risk factors for urolithiasis in patients with Crohn's disease

OBJECTIVE

To study the risk factors for urolithiasis in patients with Crohn's disease.

METHODS

This retrospective study included 1071 patients with Crohn's disease who were treated at a single center. Data pertaining to the following variables were analyzed: sex; age; type of Crohn's disease; number of intestinal resections; residual small intestine length; ileostomy; history of glucocorticoid therapy; and duration of Crohn's disease treatment.

RESULTS

Of the 1071 patients, 34 (28 male and six female) had urolithiasis (urolithiasis group) and 1037 (711 male and 326 female) did not (non-urolithiasis group). The median residual small intestine length measured in the urolithiasis group (280.0 cm) was significantly shorter than that in the non-urolithiasis group (342.5 cm; P < 0.01). Significantly more patients in the urolithiasis group (14/34) received steroid medication than those in the non-urolithiasis group (213/1037; P < 0.01). On multivariate analysis, male sex (odds ratio 3.15; P < 0.05), history of glucocorticoid therapy (odds ratio 3.07; P < 0.05), and shorter residual small intestine length (odds ratio 0.99; P < 0.01) were risk factors for the development of urolithiasis in patients with Crohn's disease.

CONCLUSION

Our results suggest that male sex, history of glucocorticoid therapy, and shorter residual small intestine length are risk factors for urolithiasis in patients with Crohn's disease.

Renal lithiasis and inflammatory bowel diseases, an update on pediatric population

BACKGROUND AND AIM OF THE WORK

Historical studies have demonstrated that the prevalence of symptomatic nephrolithiasis is higher in patients with inflammatory bowel disease (IBD), compared to general population. The aim of the review was to analyze literature data in order to identify the main risk conditions described in literature and the proposed treatment.

METHODS

A research on the databases PubMed, Medline, Embase and Google Scholar was performed by using the keywords "renal calculi/lithiasis/stones" and "inflammatory bowel diseases". A research on textbooks of reference for Pediatric Nephrology was also performed, with focus on secondary forms of nephrolithiasis.

RESULTS

Historical studies have demonstrated that the prevalence of symptomatic nephrolithiasis is higher in patients with inflammatory bowel disease (IBD), compared to general population, typically in patients who underwent extensive small bowel resection or in those with persistent severe small bowel inflammation. In IBD, kidney stones may arise from chronic inflammation, changes in intestinal absorption due to inflammation, surgery or intestinal malabsorption. Kidney stones are more closely associated with Crohn's Disease (CD) than Ulcerative Colitis (UC) in adult patients for multiple reasons: mainly for malabsorption, but in UC intestinal resection may be an additional risk. Nephrolithiasis is often under-diagnosed and might be a rare but noticeable extra-intestinal presentation of pediatric IBD. Secondary enteric hyperoxaluria the main risk factor of UL in IBD, this has been mainly studied in CD, whether in UC has not been completely explained. In the long course of CD recurrent urolithiasis and calcium-oxalate deposition may cause severe chronic interstitial nephritis and, as a consequence, chronic kidney disease. ESRD and systemic oxalosis often develop early, especially in those patients with multiple bowel resections. Even if we consider that many additional factors are present in IBD as hypomagnesuria, acidosis, hypocitraturia, and others, the secondary hyperoxaluria seems to finally have a central role. Some medications as parenteral vitamin D, long-term and high dose steroid treatment, sulfasalazine are reported as additional risk factors. Hydration status may also play an important role in this process. Intestinal surgery is a widely described independent risk factor. Patients with ileostomy post bowel resection may have relative dehydration from liquid stool, which, added to the acidic pH from bicarbonate loss, is responsible for this process. In this acidic pH, the urinary citrate level excretion reduces. The stones most commonly seen in these patients contain uric acid or are mixed. In addition, the risk of calcium containing stones also increases with ileostomy. The treatment of UL in IBD involves correction of the basic gastrointestinal tract inflammation, restricted dietary oxalate intake, and, at times, increased calcium intake. Citrate therapy that increases both urine pH and urinary citrate could also provide an additional therapeutic benefit. Finally, patients with IBD in a pediatric study had less urologic intervention for their calculosis compared with pediatric patients without IBD.

Urolithiasis in inflammatory bowel disease and bariatric surgery

AIM

To analyse current literature focusing on pathogenesis and therapeutic aspects of urolithiasis with inflammatory bowel disease (IBD) and following bariatric surgery.

METHODS

A systematic literature search was performed using PubMed, supplemented with additional references. Studies assessing the association of IBD or bariatric surgery with renal stones in both paediatric and adulthood were included.

RESULTS

Certain types of stones are seen more frequently with IBD. Hyperoxaluria and hypocitraturia are the main metabolic changes responsible for urolithiasis. The incidence of renal stones in malabsorptive types of bariatric surgery such as gastric bypass is high; this is not as common in modern restrictive surgical methods. Preventative methods and urine alkalinisation have been shown to be beneficial.

CONCLUSION

Both conditions are associated with renal stones. Patients’ counselling and prevention strategies are the mainstay of urolithiasis management in these patients.

Idiopathic hypercalciuria and formation of calcium renal stones

The most common presentation of nephrolithiasis is idiopathic calcium stones in patients without systemic disease. Most stones are primarily composed of calcium oxalate and form on a base of interstitial apatite deposits, known as Randall's plaque. By contrast some stones are composed largely of calcium phosphate, as either hydroxyapatite or brushite (calcium monohydrogen phosphate), and are usually accompanied by deposits of calcium phosphate in the Bellini ducts. These deposits result in local tissue damage and might serve as a site of mineral overgrowth. Stone formation is driven by supersaturation of urine with calcium oxalate and brushite. The level of supersaturation is related to fluid intake as well as to the levels of urinary citrate and calcium. Risk of stone formation is increased when urine citrate excretion is <400 mg per day, and treatment with potassium citrate has been used to prevent stones. Urine calcium levels >200 mg per day also increase stone risk and often result in negative calcium balance. Reduced renal calcium reabsorption has a role in idiopathic hypercalciuria. Low sodium diets and thiazide-type diuretics lower urine calcium levels and potentially reduce the risk of stone recurrence and bone disease.

Urolithiasis and crohn's disease

Objective:

To present an updated description of the relation between Crohn's disease (CD) and Urolithiasis.

Patients and Methods:

A literature search for English-language original and review articles was conducted in Medline, Embase, and Cochrane databases in the month of December 2014 for papers either published or e-published up to that date, addressing the association between CD and urolithiasis as its consequence. All articles published in English language were selected for screening based on the following search terms: “CD,” “renal calculus,” “IBD,” and “urolithiasis.” We restricted the publication dates to the last 15 years (2000–2014).

Results:

In total, 901 patients were included in this review of which 95 were identified as having CD and urolithiasis simultaneously, for a total of 10.5%. Average age was 45.07 years old, irrespective of gender. 28.6% of patients received some kind of medical intervention without any kind of surgical technique involved, 50% of patients were submitted to a surgical treatment, and the remaining 21.4% were submitted to a combination of surgical and medical treatment. Urolithiasis and pyelonephritis incidence ranged from 4% to 23% with a risk 10–100 times greater than the risk for general population or for patients with UC, being frequent in patients with ileostomy and multiple bowel resections. We found that urolithiasis occurred in 95 patients from a total of 901 patients with CD (10.5%); 61.81% in men and 38.19% in women. Stone disease seems to present approximately 4–7 years after the diagnosis of bowel disease and CaOx seems to be the main culprit.

Conclusions:

CD is a chronic, granulomatous bowel disease, with urolithiasis as the most common extraintestinal manifestation (EIM), particularly frequent in patients submitted to bowel surgery. This complication needs to be recognized and addressed appropriately, especially in patients with unexplained renal dysfunction, abdominal pain, or recurrent urinary tract infection. We believe this study to be an updated valuable review as most data related to this kind of EIM refers to articles published before 2000, most of them before 1990. These patients need to be followed up with a specific prevention plan to eliminate or mitigate the risk factors for stone disease, aiming at preventing its formation and its complications, preserving renal function, reducing morbidity, and ultimately improving their quality of life.

Dietary recommendations and treatment of patients with recurrent idiopathic calcium stone disease

This review describes the various dietary regimens that have been used to advise patients on how to prevent the recurrence of their calcium-containing kidney stones. The conclusion is that although there is some general advice that may be useful to many patients, it is more efficacious to screen each patient individually to identify his/her main urinary, metabolic, nutritional, environmental, and lifestyle risk factors for stone-formation and then tailor specific advice for that particular patient based on the findings from these investigations. If the patient can be motivated to adhere strictly to this conservative approach to the prophylactic management of their stone problem over a long time period, then it is possible to prevent them from forming further stones. This approach to stone management is considerably less expensive than any of the procedures currently available for stone removal or disintegration. In the UK, for each new stone episode prevented by this conservative approach to prophylaxis it is calculated to save the Health Authority concerned around £2000 for every patient treated successfully. In the long term, this accumulates to a major saving within each hospital budget if most stone patients can be prevented from forming further stones and when the savings are totalled up country-wide saves the National Exchequer considerable sums in unclaimed Sick Pay and industry a significant number of manpower days which would otherwise be lost from work. It is also of immense relief and benefit to the patients not to have to suffer the discomfort and inconvenience of further stone episodes.

The management of patients with enteric hyperoxaluria

Enteric hyperoxaluria is a common occurrence in the setting of fat malabsorption, usually due to intestinal resection or intestinal bypass surgery. Enhanced intestinal absorption of dietary oxalate leads to elevated renal oxalate excretion, frequently in excess of 100 mg/d (1.14 mmol/d). Patients are at increased risk of urolithiasis and loss of kidney function from oxalate nephropathy. Fat malabsorption causes increased binding of diet calcium by free fatty acids, reducing the calcium available to precipitate diet oxalate. Delivery of unabsorbed bile salts and fatty acids to the colon increases colonic permeability, the site of oxalate hyper-absorption in enteric hyperoxaluria. The combination of soluble oxalate in the intestinal lumen and increased permeability of the colonic mucosa leads to hyperoxaluria. Dietary therapy consists of limiting oxalate and fat intake. The primary medical intervention is the use of oral oxalate binding agents such as calcium salts to reduce free intestinal oxalate levels. Bile acid sequestrants can be useful in patients with ileal resection and bile acid malabsorption. Oxalate degrading bacteria provided as probiotics are being investigated but as of yet, no definite benefit has been shown with currently available preparations. The current state of medical therapy and potential future directions will be summarized in this article.