Renal Medullary Pyramids Research Articles

Renal Papillary Necrosis (RPN) in an African Population: Disease Patterns, Relevant Pathways, and Management.

Renal papillary necrosis (RPN) is characterized by coagulative necrosis of the renal medullary pyramids and papillae. Multiple conditions and toxins are associated with RPN. Several RPN risk factors, or POSTCARDS, have been identified, with most patients presenting with RPN having at least two contributing risk factors. Currently, there is no specific test to diagnose and confirm RPN; however, several imaging tools can be used to diagnose the condition. RPN is currently underdiagnosed in African populations, often with fatal outcomes. In African clinical settings, there is a lack of consensus on how to define and describe RPN in terms of kidney anatomy, pathology, endourology, epidemiology, the identification of African-specific risk factors, the contribution of oxidative stress, and lastly an algorithm for managing the condition. Several risk factors are unique to African populations including population-specific genetic factors, iatrogenic factors, viral infections, antimicrobial therapy, schistosomiasis, substance abuse, and hypertension (GIVASSH). Oxidative stress is central to both GIVASSH and POSTCARDS-associated risk factors. In this review, we present information specific to African populations that can be used to establish an updated consensual definition and practical grading system for radiologists, urologists, nephrologists, nuclear physicians, and pathologists in African clinical settings.

SAT-356 Reversible Suppression of Serum 1,25-Dihydroxyvitamin D in Williams Syndrome

Background: Hypercalcemia has been reported in 5% to 50% of patients with Williams syndrome; however, observations about the role of 1,25-dihydroxyvitamin D in hypercalcemia related to Williams syndrome have been contradictory. Objective: The objective was to investigate the mineral metabolism in an 11-month-old patient with Williams-Beuren syndrome who had hypercalcemia, hypercalciuria and nephrocalcinosis. Methods: We reviewed test results in an 11-month-old infant with Williams syndrome who developed hypercalcemia following excessive dietary calcium intake that was two to three times higher than recommended for age because he continued receiving a premature formula with high calcium content from birth. Results: Our patient presented with feeding difficulties, daily vomiting, weight loss, and constipation. He had serum total calcium 14.8 mg/dL, phosphorus 4.0 mg/dL, PTH <4 pg/mL, 1,25-dihydroxyvitamin D <8 pg/mL, 25-hydroxyvitamin D 29 ng/mL, PTH-related peptide 3.7 pmoL/L (expected <4.2), alkaline phosphatase 118 U/L, beta-crosslaps 1257 pg/mL, and urinary calcium/creatinine ratio 1.19. XR Skeletal Survey revealed increased bone density in the metaphyseal regions, in particular, above the knee, distal radius and ulna that may result from hypercalcemia; no evidence of rickets, osteoporosis or congenital osteodystrophy was seen. Renal ultrasound revealed increased echogenicity of the renal medullary pyramids consistent with medullary nephrocalcinosis. Hypercalcemia and hypercalciuria were initially treated with IV fluids and Furosemide IV, and resolved only after Pamidronate 0.5 mg/kg/dose IV x 2 doses. After serum calcium normalized, the patient’s symptoms resolved, PTH recovered to 18 pg/mL (expected 10 - 65), and 1,25-dihydroxyvitamin D increased to 27 pg/mL (expected 24 - 86). Chromosomal micro-array analysis showed a 1.9 megabase deletion at 7q11.23 that overlapped the Williams syndrome critical region including the ELN gene, consistent with diagnosis of Williams syndrome. Serum calcium remained normal with dietary calcium restriction using a low-calcium formula and complementary foods. Conclusions: PTH-independent hypercalcemia in our patient with Williams syndrome was due to calcium overload resulting from dietary calcium excess in addition to possibly enhanced intestinal calcium absorption. Serum 1,25-dihydroxyvitamin D was undetectable and returned to normal only with resumption of PTH secretion required for its synthesis after hypercalcemia resolved. The balance between bone formation and resorption was shifted to resorption possibly to remove skeletal calcium excess, based on normal alkaline phosphatase (marker of osteoblast activity) and high collagen beta-crosslaps (marker of osteoclast activity). A premature formula with high calcium content should be switched to a full-term formula when risk for rickets of prematurity clears.

SAT-363 Renal Papillary Necrosis Associated with Normocalcemic Hyperparathyroidism

IntroductionHypercalciuria is generally considered to be the most common identifiable metabolic risk factor for calcium nephrolithiasis. Important renal manifestations of primary hyperparathyroidism (PHPT) include asymptomatic nephrolithiasis, hypercalciuria, nephrocalcinosis, and chronic renal insufficiency. However renal papillary necrosis (RPN) occurring in PHPT has not been reported previously. We report a 50-year-old woman who manifested RPN associated with hypercalciuria and normocalcemic PHPT. Case ReportA 50-year-old Caucasian woman was evaluated in 2006 for hypercalcemia. She had no history of nephrolithiasis, fractures, or symptoms of hypercalcemia. Laboratory: serum calcium 11.8 mg/dL, ionized calcium 6.3 mg/dL, phosphorus 1.8 mg/dL, intact PTH 98 pg/mL (ref 15–65), urine calcium 543 mg/24 hrs (ref <235). Renal ultrasound showed no evidence of nephrocalcinosis or nephrolithiasis. A parathyroid scan was consistent with a left superior parathyroid adenoma. Patient underwent parathyroidectomy and became normocalcemic with normal serum PTH levels postoperatively. One year later she was diagnosed with a left sided bronchial carcinoid tumor. Surveillance Gallium-68 PET/CT scan done 2 years later was negative for any metastases. Twelve years later she reported to our clinic for follow up. She had no symptoms of hypercalcemia, fractures, nephrolithiasis, history of pyelonephritis, diabetes mellitus, analgesic use, or hypertension. Serum calcium was 9.1 mg/dL, serum phosphorous 3.8mg/dL, PTH 82 pg/mL, 25-OH vitamin D 34 ng/mL, 1,25-vitamin D 38 pg/mL, and a urorisk panel was normal except for a 24-hour urine calcium of 410 mg. However renal ultrasound showed bilateral RPN and this diagnosis was also confirmed by a CT scan. A urinalysis showed only microalbuminuria with no red cells. She had no history of any analgesic drug abuse, pyelonephritis, sickle cell disease, or diabetes mellitus. A glucose tolerance test was completely normal. Discussion RPN is characterized by coagulative necrosis of the renal medullary pyramids and papillae brought on by several associated disorders and toxins that exhibit synergism toward the development of ischemia. Although the initial kidney US was normal, a repeat US done 12 years later showed evidence of RPN. This finding along with hypercalciuria and a diagnosis of normocalcemic PHPT suggests that RPN may be associated with hypercalciuria and normocalcemic PHPT. Furthermore she had no other risk factors for RPN. Additional studies with large number of patients are needed to confirm the association between these 2 disorders.

Rare variant of Lesch–Nyhan syndrome without self-mutilation or nephrolithiasis

Lesch-Nyhan syndrome is a very rare X-linked recessive disorder characterized by mental retardation, spasticity resembling cerebral palsy, choreo-athetosis, self-mutilation and hyperuricemia. Self-mutilative behavior is a hallmark of the disease. Hyperuricemia leads to hyperuricuria and uric acid nephrolithiasis. The underlying defect is a deficiency of hypoxanthine-guanine-phosphoribosyl transferase. We report on a 7-year-old boy with Lesch-Nyhan syndrome, lacking self-mutilative behavior, who was erroneously diagnosed as having athetotic cerebral palsy. He also had no renal stones; hyperechoic renal medullary pyramids were the only renal abnormality detected and were sonographically indistinguishable from medullary nephrocalcinosis.

Transient hyperechogenicity of the renal medullary pyramids: incidence in the healthy term newborn.

A screening program was performed on 1881 clinically healthy term newborns, aimed at detecting eventual pathological conditions not diagnosed during pregnancy. Seventy-three cases of transient hyperechogenicity of the renal medullary pyramids were observed, involving one or both kidneys with either sectorial or diffuse pattern. None of the neonates examined had evidence of renal dysfunction and follow-up ultrasound scans demonstrated complete resolution of the sonographic picture. Medullary hyperechogenicity is not rare in healthy term newborns (3.9%); it presents rapid resolution and should be considered in differential diagnosis of pathological conditions.

Serial renal sonographic evaluation of patients with Lesch-Nyhan syndrome.

The objective of this study was to review sequential renal sonograms of patients with Lesch-Nyhan syndrome obtained over several years to determine different sonographic patterns, the alterations in the patterns occurring over time and the relationship to management. Additional objectives were to evaluate the size of the kidneys, and to correlate the metabolic constituents of calculi with the therapeutic regimens and with the renal sonographic patterns. Serial sonograms of six patients with Lesch-Nyhan syndrome were reviewed for periods varying between 2 and 7 years with a mean of 4 years. The ages of the patients at the conclusion of the study were between 10 and 22 years. Three patterns of abnormal echogenicity were found; a punctate increase in echogenicity in the renal medullary pyramids, a diffuse increase in medullary pyramid echogenicity, and a pattern of increased echogenicity in the collecting system. These patterns were progressive but did not alternate on sequential scans, regardless of increasing or constant therapy. Analysis of calculi suggested patients were precipitating various metabolites concurrently; the incidence of metabolites appeared to be unrelated to therapy. Those patients with shadowing opacities, whether in the renal medulla or collecting system, were more likely to develop renal colic. Renal dimensions were small with renal function remaining normal.

Ultrasonographic examination of the left kidney, the urinary bladder, and the urethra in cows.

The purpose of the present study was to determine the position, dimensions and structure of the left kidney, the urinary bladder and the urethra in cattle by use of ultrasonography. The left kidney, the urinary bladder and the urethra of 12 healthy, Swiss Braunvieh cows were examined transrectally using a 5.0 MHz linear transducer 10 times within two weeks. The lobulation of the kidney in cattle could be visualized ultrasonographically. The echogenicity of various renal structures differed. The renal cortex was hyperechoic in comparison to the relative hypoechoic renal medullary pyramids. The urinary bladder was always visible but its diameter varied greatly. The vertical diameter of the left kidney was 6.2 +/- 1.0 cm in the region of the renal hilus. In 7 cows the thickness of renal cortex and medulla was between 2.0 and 2.3 cm. The diameter of the renal sinus varied from 1.1 to 2.5 cm. The interassay coefficients of variation of the variables measured varied between 8.5 and 16.5%. It was concluded that the ultrasonographic values determined in this study can be used as references for the diagnosis of morphologic changes in the bovine left kidney.

Hyperechoic renal medullary pyramids in infants and children.

Fifty-five children (34 boys, 21 girls; age range, 1 day to 18 years) with increased echogenicity of the renal medullary pyramids at ultrasound evaluation were identified. The clinical diagnoses associated with hyperechoic medullary pyramids could be separated based on the presence or absence of hypercalciuria. Patients with drug-induced hypercalciuria included 10 infants treated with furosemide, two treated with long-term steroid therapy, and one treated with excessive amounts of vitamin D. Other clinical conditions associated with hypercalciuria included renal tubular acidosis (n = 10), Bartter syndrome (n = 5), hyperparathyroidism (n = 3), Williams syndrome (n = 2) and medullary sponge kidney (n = 2). Ten children with transient renal insufficiency and three with sickle cell disease had normal urine calcium concentration. Isolated disease entities accounted for the remainder of cases. A specific diagnosis can usually be made in a patient with hyperechoic renal medullary pyramids by using a systematic clinical approach that includes evaluation of patient age, serum and urine calcium concentration, and renal function.

Hyperechoic renal medullary pyramids in infants and children.

Hyperechoic renal medullary pyramids in infants and children.

Hyperechogenic "rings" in the periphery of renal medullary pyramids as a sign of renal disease.

A rare sign of medullary abnormality, hyperechogenic "rings" in the peripheries of renal medullary pyramids, was detected in both kidneys in 21 patients, being associated with normally hypoechogenic medullary centers in 20 of these patients. Our results with 2 cases studied histologically suggest that fibrosis with and without calcifications is one reason for the hyperechogenicity of these medullary pyramids. The clinical history and laboratory tests (serum creatinine, proteinuria) showed signs of kidney disease in 52%, and a renal disease was suspected in an additional 38%. Eight of the patients had disturbances in blood potassium, calcium, or uric acid equilibrium, and 2 of them had a parathyroid abnormality. Calcifications were found on plain radiographs of the abdomen in 1 of the 13 patients. Two were totally asymptomatic and had normal laboratory findings. Hyperechogenic rings in the peripheries of renal medullary pyramids proved nonspecific and showed a poor correlation with the severity of renal disease.