The use of a pelvic displacement prosthesis to exclude the small intestine from the radiation field following radical hysterectomy.

OBJECTIVE: The goal of this study was to develop a device which will elevate the small intestine out of the pelvic cavity during radiation after radical surgery. METHODS: A prosthetic device of silicone plastic was designed which conforms to the pelvis. This device is filled with saline and renograffin for X-ray visualization. The capacity of the device is between 750 and 1500 cc. A small bowel contrast radiograph is performed prior to radiation to document exclusion from the radiation field. The device remains in place throughout radiation therapy and is then removed through a small incision after draining the contents of the prosthesis. RESULTS: Seven devices have been placed to date. The patients' age ranged from 35 to 65 years. All women had stage Ib1 carcinoma of the cervix and all underwent a type III radical hysterectomy with bilateral pelvic and common iliac lymphadenectomy. The indication for placement of the device was deep invasion of tumor in five patients, close margin in one patient, and positive pelvic lymph nodes in one patient. The amount of fluid instilled in the device ranged from 960 to 1200 cc. All patients had a return to normal bowel function within 3 days of surgery. All had radiologically documented exclusion of the small intestine from the radiation field prior to beginning radiation. In the postoperative period there was one major complication: a pulmonary embolism documented by pulmonary angiogram on postoperative day 2. All seven patients completed planned radiotherapy. The devices have been removed, with no adhesions to the prosthesis. CONCLUSIONS: The results of this study determine that the feasibility, safety, and efficacy of a prosthetic device in displacing the small bowel from the radiation field following radical surgery are sufficient to warrant a large-scale study. The device should be applicable to any and all tumors that require high dose pelvic radiation. It is expected that displacement of the small intestine from the radiation field will diminish overall complications and may allow delivery of radiation doses that approach colon and bladder tolerance.

Prevention of recurrent nephrolithiasis.

The first episode of nephrolithiasis provides an opportunity to advise patients about measures for preventing future stones. Low fluid intake and excessive intake of protein, salt and oxalate are important modifiable risk factors for kidney stones. Calcium restriction is not useful and may potentiate osteoporosis. Diseases such as hyperparathyroidism, sarcoidosis and renal tubular acidosis should be considered in patients with nephrolithiasis. A 24-hour urine collection with measurement of the important analytes is usually reserved for use in patients with recurrent stone formation. In these patients, the major urinary risk factors include hypercalciuria, hyperoxaluria, hypocitraturia and hyperuricosuria. Effective preventive and treatment measures include thiazide therapy to lower the urinary calcium level, citrate supplementation to increase the urinary citrate level and, sometimes, allopurinol therapy to lower uric acid excretion. Uric acid stones are most often treated with citrate supplementation. Data now support the cost-effectiveness of evaluation and treatment of patients with recurrent stones.

Reduced crystallization inhibition by urine from men with nephrolithiasis.

BACKGROUND: Human urine is known to inhibit growth, aggregation, nucleation, and cell adhesion of calcium oxalate monohydrate (COM) crystals, the main solid phase of human kidney stones. This study tests the hypothesis that low levels of inhibition are present in men with calcium oxalate stones and could therefore promote stone production. METHODS: In 17 stone-forming men and 17 normal men that were matched in age to within five years, we studied the inhibition by dialyzed urine proteins of COM growth, aggregation, and binding to cultured BSC-1 renal cells, as well as whole urine upper limits of metastability (ULM) for COM and calcium phosphate (CaP) in relationship to the corresponding supersaturation (SS). RESULTS: Compared with normals, patient urine showed reduced COM growth inhibition and reduced ULM in relationship to SS. When individual defects were considered, 15 of the 17 patients were abnormal in one or more inhibition measurements. ULM and growth inhibition defects frequently coexisted. CONCLUSIONS: Reduced COM growth and CaP and CaOx ULM values in relationship to SS are a characteristic of male stone formers. Both defects could promote stones by facilitating crystal nucleation and growth. Abnormal inhibition may be a very important cause of human nephrolithiasis.

Evidence that calgranulin is produced by kidney cells and is an inhibitor of calcium oxalate crystallization.

Urine produced by normal human kidneys is almost always supersaturated with respect to calcium oxalate (CaOx), the most common constituent of human kidney stones. Crystallization, with risk of renal damage and kidney stones, appears to be affected by molecules in urine that retard nucleation, growth, aggregation, and renal cell adherence of CaOx. The repertoire of such molecules is incompletely known. We have purified a 28-kDa protein from urine using salt precipitation, preparative isoelectric focusing, and sizing chromatography. Amino acid composition and NH2-terminal amino sequence analysis showed complete homology to calgranulin. Calgranulin was found to be a potent inhibitor of CaOx crystal growth (44% of control) and aggregation (50% of control) in the nanomolar range. Calgranulin cDNA was cloned from a human kidney expression library. Western analysis of human and rat kidney homogenates and mRNA temporal expression from two independent renal epithelial cell lines showed that calgranulin is produced in the kidney. Given its urinary abundance and potency, calgranulin may contribute importantly to the normal urinary inhibition of crystal growth and aggregation and therefore to the renal defense against clinical stone disease.

Dependence of upper limit of metastability on supersaturation in nephrolithiasis.

Formation of renal stones requires supersaturation (SS) high enough to induce crystallization; such a SS is referred to as the upper limit of metastability (ULM). The ULM for calcium oxalate (CaOx) or calcium phosphate can be measured by adding oxalate or calcium to urine, respectively, and noting the point at which overt crystallization occurs as evidenced by clouding. In principle, the urine should be more prone to form stone crystals as its SS approaches the ULM, and the SS ULM distance has been used as an index of stone forming potential. In addition, one would expect the ULM and initial SS to be unrelated, as the starting urine SS has no apparent link to the amount of calcium or oxalate that urine can dissolve without leading to crystal formation. However, in rats, we have found a surprising correlation between ULM and SS, such that ULM appears to rise with initial SS, for CaOx, and, to a lesser extent, for brushite (Br), a typical calcium phosphate initial phase. In this study, we measured CaOx and Br ULM, and SS, in urine of 50 patients and 11 normal people, to determine if ULM and SS were correlated, as in rats, and to explore the relationship between SS and ULM. We found the same dependence of ULM on SS as in rats, for both CaOx and Br, and found no differences between patients and normal people with respect to this dependency. However, for Br, patients showed a lower ULM than normals, but the same initial SS, meaning that patients were closer to their crystal formation threshold than normals. Treatments for stones had no apparent effect on the SS-ULM dependency. We conclude that in humans, as in rats, ULM is related to initial SS, and that this relationship is the same in patients as in normals for CaOx, but shifted in a stone forming direction for Br among patients. The ULM-SS interaction is unaffected by contemporary conventional stone treatments, and is more marked for CaOx than Br. The mechanisms of the dependence are unknown. The smaller difference between ULM and initial SS for Br in patients than normal supports prior evidence suggesting a defect in stone patients that could lead to calcium phosphate crystallization, subsequent nucleation of CaOx, and stone disease.

Increased urinary saturation and kidney calcium content in genetic hypercalciuric rats.

We have established a colony of genetic hypercalciuric (IH) rats as a model of idiopathic hypercalciuria in humans. To test the hypothesis that hypercalciuria can cause crystallization in kidneys through increased supersaturation, in the absence of confounding effects of diet and whatever complex inhibitor disorders underlay stone disease, we fed males and females of the 21st generation of IH rats 13 g per day of a low calcium (LCD, 0.02% Ca), followed by a normal calcium (NCD, 0.6% Ca) and then a high calcium (HCD, 1.2% Ca) diet, each for seven days. During the last 24 hours of each period complete urine collections were obtained and analyzed for all substances known to affect urinary calcium oxalate (CaOx) and brushite (CaHPO4) supersaturation. Relative supersaturation with respect to the solid phases of CaOx and CaHPO4 were then calculated. Compared to same gender controls (Ctl) urine calcium excretion was higher in the female IH rats on all diets and in the male IH rats on NCD and HCD. The female and male IH rats on NCD and HCD were supersaturated with respect to CaOx; however, the male and female Ctl were supersaturated with respect CaOx only on HCD. The female IH rats on NCD and HCD and the male IH rats on NCD were supersaturated with respect to CaHPO4; however, neither the male nor female Ctl rats were supersaturated with respect to CaHPO4 on any diet. On NCD and HCD urine supersaturation with respect to CaHPO4 by females exceeded that of males.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that mouse renal proximal tubule cells produce nephrocalcin.

Nephrocalcin (NC) is a glycoprotein inhibitor of calcium oxalate monohydrate crystal growth present in urine and kidney tissue. To determine if kidney cells can produce NC, we have isolated proximal tubules from mouse kidney and cultured them in a serum-free medium containing supplements. The tubules accumulate p-aminohippurate and respond with increase in adenosine 3',5'-cyclic monophosphate to parathyroid hormone but not to arginine vasopressin. They produce 1,25 dihydroxyvitamin D3 when 25 hydroxyvitamin D3 is added as substrate. Medium conditioned for 3 days reacted by direct enzyme-linked immunosorbent assay (ELISA) with a rabbit antiserum to human urinary NC; the same antiserum was localized to the cells using immunoperoxidase staining. Using ion exchange and molecular sieve chromatography, we purified a glycoprotein calcium oxalate crystal-growth inhibitor the chromatographic behavior and amino acid and carbohydrate compositions of which closely resembled that of purified human urinary NC. Its dissociation constant toward the calcium oxalate crystal was 0.4-10 X 10(-7) M. Purified fractions of the protein cross-reacted with the antiserum tested by ELISA. Cultured proximal tubule cells produce a molecule that resembles NC from human urine, rat urine, and rat kidneys; proximal tubule is a probable site of NC production in vivo.

Ca and P regulation of 1,25(OH)2D3 synthesis by vitamin D-replete rat tubules during acidosis.

Elevated blood ionized Ca concentration appears to be necessary for suppression by chronic metabolic acidosis (CMA) of serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] levels in vitamin D-replete rats eating a low-Ca diet (LCD). The present study asks whether in vitro 1,25(OH)2D3 production by proximal tubule cells from such rats is suppressed and whether suppression can be reversed in vitro by an altered ionic milieu. Young rats were fed LCD and given 1.5% NH4Cl in their drinking water for 10 days to produce CMA. Compared with controls, CMA rats had low serum 1,25(OH)2D3 levels. Tubules prepared from CMA rats produced 1,25(OH)2D3 at a low rate compared with control; variation of medium Ca and pH from 7.2 to 7.4 did not increase 1,25(OH)2D3 production. Reducing medium phosphorus concentration ([P]) increased 1,25(OH)2D3 production by tubules from control but not CMA rats. Increasing medium [P] increased 1,25(OH)2D3 production by tubules from CMA but not control rats. CMA appears to alter proximal tubule cell response to medium [P] so that 1,25(OH)2D3 production rises when medium [P] is increased but not when it is reduced. Medium pH and Ca concentration do not appear to be important regulators of renal 1,25(OH)2D3 production in short-term incubations.

Mechanism of chronic hypercalciuria with furosemide: increased calcium absorption.

Furosemide produces chronic hypercalciuria. The source of the additional urinary calcium is not known but must be either bone mineral or calcium absorbed by the intestine. Without bone calcium dissolution or increased absorption the filtered load of calcium would fall and urinary calcium excretion would return to pretreatment levels. To determine whether furosemide alters intestinal calcium absorption, we fed furosemide (75 mg . kg body-1 wt . day-1) to 11 rats eating 15 g/day of a 0.60% calcium diet. Compared with 11 control rats, furosemide increased urine calcium (15.6 +/- 0.8 mg/5 days vs. 4.1 +/- 0.3, P less than 0.001). Fecal calcium excretion fell (194 +/- 7 mg/5 days vs. 223 +/- 12, P less than 0.05), indicating an increase in intestinal calcium absorption sufficient to sustain the hypercalciuria. The increase in absorption occurred without an increase in the level of serum 1,25-dihydroxycholecalciferol (180 +/- 20 pg/ml vs. 220 +/- 16, furosemide vs. control, respectively, P = NS). To determine whether the intestinal effect of furosemide persists after the initial sodium diuresis abates, we analyzed only the last 3 days of balance. Again, rats fed furosemide had increased urine excretion and intestinal absorption of calcium, so that net calcium balance was not different from that of controls. Twelve additional rats were fed a 0.02% calcium diet to which 35 mg . kg body wt-1 . day-1 of furosemide was added. Compared with eleven controls, urine calcium increased and fecal calcium excretion again fell, but balance was not different. Chronic administration of furosemide increases intestinal calcium absorption enough to permit urine calcium excretion to remain elevated without the necessity for bone dissolution.

Evidence that blood ionized calcium can regulate serum 1,25(OH)2D3 independently of parathyroid hormone and phosphorus in the rat.

This study asks whether arterial blood ionized calcium concentration (Ca++) can regulate the serum level of 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] independently of serum phosphorus and parathyroid hormone (PTH). We infused either PTH (bovine 1-34, 10 U/kg body wt/h) or saline into awake and unrestrained rats for 24 h, through a chronic indwelling catheter. PTH raised total serum calcium and arterial blood ionized calcium, yet serum 1,25(OH)2D3 fell from 35 +/- 6 (mean +/- SEM, n = 10) with saline to 12 +/- 3 pg/ml (n = 11, P less than 0.005 vs. saline). To determine if the decrease in serum 1,25(OH)2D3 was due to the elevated Ca++, we infused PTH into other rats for 24 h, along with varying amounts of EGTA. Infusion of PTH + 0.67 micron/min EGTA reduced Ca++, and 1,25(OH)2D3 rose to 90 +/- 33 (P less than 0.02 vs. PTH alone). PTH + 1.00 micron/min EGTA lowered Ca++ more, and 1,25(OH)2D3 increased to 148 +/- 29 (P less than 0.01 vs. saline or PTH alone). PTH + 1.33 micron/min EGTA lowered Ca++ below values seen with saline or PTH alone, and 1,25(OH)2D3 rose to 267 +/- 46 (P less than 0.003 vs. all other groups). Thus, during PTH infusion lowering Ca++ with EGTA raised 1,25(OH)2D3 progressively. There were no differences in serum phosphorus concentration or in arterial blood pH in any group infused with PTH. The log of serum 1,25(OH)2D3 was correlated inversely with Ca++ in all four groups infused with PTH (r = -0.737, n = 31, P less than 0.001), and also when the saline group was included (r = -0.677, n = 41, P less than 0.001). The results of this study indicate that serum 1,25(OH)2D3 may be regulated by Ca++ independent of PTH and serum phosphorus levels in the rat. Since 1,25(OH)2D3 regulates gastrointestinal calcium absorption, there may be direct feedback control of 1,25(OH)2D3, by its regulated ion, Ca++.

Response of serum 1,25(OH)2D3 to variation of ionized calcium during chronic acidosis.

Chronic ammonium chloride (NH4Cl) administration causes metabolic acidosis and prevents the normal rise of serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] during a low-calcium diet (LCD, 0.002% calcium). The suppression of serum 1,25(OH)2D3 was not due to reduced parathyroid hormone concentration, elevated serum phosphorus, or total calcium concentration. Acidosis increased blood ionized Ca [Ca2+] and proton [H+] concentrations. Serum 1,25(OH)2D3 levels were inversely correlated with both [Ca2+] and [H+]. To determine the independent effects of [Ca2+] on serum 1,25(OH)2D3 we varied [Ca2+] at a constant [H+] by infusing either EGTA or saline for 24 h after 11 days of LCD and NH4Cl. EGTA, preequilibrated with three concentrations of Ca, lowered [Ca2+] and raised 1,25(OH)2D3 but did not alter [H+] or serum phosphorus concentration. The log of serum 1,25(OH)2D3 varied linearly and inversely with arterial blood [Ca2+] during saline (r = -0.884, n = 8, P less than 0.001) and EGTA infusions (r = -0.798, n = 22, P less than 0.001). At all levels of [Ca2+], rats infused with EGTA had a higher serum 1,25(OH)2D3 than those infused with saline. Log serum 1,25(OH)2D3 was correlated neither with [H+] nor pH. Elevated [Ca2+] and not [H+] appears to suppress the serum 1,25(OH)2D3 response to LCD during NH4Cl acidosis in the rat.

Role of fetal 1,25-dihydroxyvitamin D production in intrauterine phosphorus and calcium homeostasis.

During intrauterine life, fetal mineral accretion depends on active transfer from mother to fetus by the placenta. To evaluate the role of fetal production of 1,25-dihydroxyvitamin D in regulation of fetal phosphorus, calcium, and parathyroid homeostasis, studies were performed in ewes and their fetal lambs. Fetal nephrectomy caused a rise in fetal serum phosphorus and a fall in total calcium 5 days after nephrectomy. Fetal blood ionized calcium also fell and serum parathyroid hormone rose. In sham-nephrectomized fetuses, all four measurements were unchanged compared to control values. Simultaneous maternal values of ionized calcium were normal in control and nephrectomized fetuses. Fetal ureteral severance and drainage of urine into the fetal peritoneal cavity produced none of the effects of fetal nephrectomy. Daily intravenous injection of 1,25-dihydroxyvitamin D into fetuses after nephrectomy prevented the rise in serum phosphate, and serum calcium did not fall. The results suggest that fetal 1,25-dihydroxyvitamin D regulates fetal phosphate homeostasis, perhaps by the placenta, which in turn regulates blood-ionized calcium concentration.

Mechanism of chronic hypocalciuria with chlorthalidone: reduced calcium absorption.

Chlorthalidone, like other benzothiadiazides, lowers urine calcium excretion chronically. If intestinal calcium absorption did not fall or bone accretion did not increase, serum calcium and the filtered load of calcium would increase and urine calcium would return to pretreatment levels. To determine whether overall intestinal calcium absorption fell, we fed chlorthalidone (5 mg X kg body wt-1 X 24 h-1) to 10 adult male rats eating 15 g/day of a 0.6% calcium diet. Compared with 10 control rats, chlorthalidone reduced urine calcium [2.1 +/- 0.1 (SE) vs. 5.8 +/- 0.5 mg/6 days; P less than 0.001]. Fecal calcium rose (307 +/- 9 vs. 257 +/- 12; P less than 0.005) because percent intestinal calcium absorption fell (41 +/- 2 vs. 52 +/- 2; P less than 0.002). Twenty other rats given the same diet were injected subcutaneously with 1,25(OH)2D3 (50 ng/day). In these rats, chlorthalidone reduced urine calcium (23 +/- 3 vs. 59 +/- 3; P less than 0.001) and percent intestinal calcium absorption (60 +/- 1 vs. 66 +/- 1; P less than 0.01). With or without 1,25(OH)2D3, chronic administration of chlorthalidone reduces intestinal calcium absorption, and this reduction seems to be the mechanism that permits urine calcium excretion to remain low.

Effects of low-calcium diet on urine calcium excretion, parathyroid function and serum 1,25(OH)2D3 levels in patients with idiopathic hypercalciuria and in normal subjects.

We have used a low-calcium diet providing only 2 mg/kg (body weight) per 24 hours of calcium to distinguish between "renal" and "absorptive" idiopathic hypercalciuria. Sixteen of 27 hypercalciuric subjects excreted calcium in excess of intake during days seven, eight and nine of he diet, suggesting some element of renal hypercalciuria; however, all patients had low or normal serum PTH and urine cAMP levels. In general, fasting urine calcium was elevated in these 16 subjects and normal in the remaining 11, who conserved calcium more normally. SErum 1,25(OH)2D3 levels were the same in patients and normal subjects, even though PTH levels of the patients were below those of he normal subjects. Urine magnesium excretion and phosphorus excretion were both increased in the patients who excreted calcium in excess of intake. Our findings suggest that renal and absorptive hypercalciuria may not be distinct entities but rather the two extremes of a continuum of behavior. A uniform elevation of intestinal calcium absorption and a variable defect of renal calcium reabsorption could explain our results far better than the hypothesis of distinct absorptive and renal forms of hypercalciuria.

Evidence for mild reversible hyperparathyroidism in distal renal tubular acidosis.

Circulating levels of immunoreactive parathyroid hormone were measured in six patients with distal renal tubular acidosis before and during two years of long-term alkali therapy. Parathyroid hormone level was elevated modestly in five patients before treatment and fell, gradually during treatment to normal or near normal levels. Urine calcium level fell, serum calcium level rose, and renal phosphorus reabsorption rose during treatment. Stopping treatment briefly caused reversion of serum parathyroid hormone and calcium levels and renal phosphorus reabsorption to pretreatment values within eight weeks. Mild hyperparathyroidism is present in renal tubular acidosis and reverses with alkali treatment.

Evidence for secondary hyperparathyroidism in idiopathic hypercalciuria.

Circulating levels of immunoreactive parathyroid hormone (PTH) were measured in 40 patients with idiopathic hypercalciuria (IH) before and during reversal of hypercalciuria with thiazide, and in four normal subjects before and during induction of hypercalciuria with furosemide. 26 patients with IH had elevated serum PTH levels. The remaining patients had normal levels. Although the correlation was not complete, high PTH levels were generally found in patients who had more severe average urinary calcium losses. When initially elevated. PTH levels fell to normal or nearly normal values during periods of thiazide administration lasting up to 22 months. When initially normal, PTH levels were not altered by thiazide. Reversal of hyperparathyroidism by thiazide could not be ascribed to the induction of hypercalcemia, since serum calcium concentration failed to rise in a majority of patients. Renal hypercalciuria produced by furosemide administration elevated serum PTH to levels equivalent to those observed in patients with IH. The findings in this study help to distinguish between several current alternative views of IH and its relationship to hyperparathyroidism. Alimentary calcium hyperabsorption cannot be the major cause of IH with high PTH levels, because this mechanism could not elevate PTH. Idiopathic hypercalciuria cannot be a variety of primary hyperparathyroidism, as this disease is usually defined, because PTH levels are not elevated in all patients and, when high, are lowered by reversal of hypercalciuria. Primary renal loss of calcium could explain the variable occurrence of reversible hyperparathyroidism in IH, since renal hypercalciuria from furosemide elevates serum PTH in normal subjects. Consequently, a reasonable working hypothesis is that IH is often due to a primary renal defect of calcium handling that leads, by unknown pathways, to secondary hyperparathyroidism.