Efficacy of Hounsfield Unit of CT in Prediction of the Chemical Composition of Urinary Stones

Objectives to make a reliable correlation between the chemical composition of the urinary calculi and its Hounsfield unit on CT scan, upon which we can depend on it for prediction of the type of the urinary calculi. The prediction of the chemical structure of the stone would help us to reach a more efficient therapeutic and prophylactic plan. Methods A retrospective study was performed by interpretation of the preoperative CT scans for patients who were presented by urinary stones. Identification of the chemical structure of the calculi was implemented using Fourier Transform Infrared Spectroscopy (FT-IR spectroscopy). The laboratory report revealed multiple types of stones either of pure or mixed composition. Afterwards, a comparison was done between Hounsfield units of the stones and the chemical structure. Results The chemical structure of the urinary stones revealed four pure types of stones (Uric acid, Calcium Oxalate, Struvite and Cystine) and two types of mixed stones (mixed calcium oxalate+ Uric, and mixed calcium oxalate+ calcium phosphate). Uric acid stone had a mean Hounsfield Unit (HU) density of428 ± 81, which was quite less than the other stones, followed by struvite stones with density ranging about 714 ± 38. Mixed calcium oxalate stones could be differentiated from other types of stones like uric acid, pure calcium oxalate and struvite stones by the Hounsfield unit of Computed Tomography (the mean Hounsfield Unit was 886 ± 139 and 1427 ± 152 for mixed calcium oxalate + uric stone and mixed calcium oxalate + calcium phosphate stones respectively). Moreover, pure calcium oxalate stones were easily differentiated from all other stones using the mean Hounsfield density as it was 1158 ± 83. It was challenging only when it was compared to cystine stones, as they were quiet similar to HU value (997 ± 14). The variation of Hounsfield values among the previously mentioned stones, was statistically significant (p < 0.001). Conclusion The study proved that the Hounsfield Unit of CT scanning is a convenient measure to predict the chemical structure of urinary calculi.

Stone composition of renal stone formers from different global regions

Objective: To study urinary stone composition patterns in different populations around the world. Materials and methods: Data were collected by reviewing charts of 1204 adult patients of 10 countries with renal or ureteral stones (> 18 years) in whom a stone analysis was done and available. Any method of stone analysis was accepted, but the methodology had to be registered. Results: In total, we observed 710 (59%) patients with calcium oxalate, 31 (1%) with calcium phosphate, 161 (13%) with mixed calcium oxalate/calcium phosphate, 15 (1%) with carbapatite, 110 (9%) with uric acid, 7 (< 1%) with urate (ammonium or sodium), 100 (9%) with mixed with uric acid/ calcium oxalate, 56 (5%) with struvite and 14 (1%) with cystine stones. Calciumcontaining stones were the most common in all countries ranging from 43 to 91%. Oxalate stones were more common than phosphate or mixed phosphate/oxalate stones in most countries except Egypt and India. The rate of uric acid containing stones ranged from 4 to 34%, being higher in Egypt, India, Pakistan, Iraq, Poland and Bulgaria. Struvite stones occurred in less than 5% in all countries except India (23%) and Pakistan (16%). Cystine stones occurred in 1% of cases. Conclusions: The frequency of different types of urinary stones varies from country to country. Calcium-containing stones are prevalent in all countries. The frequency of uric acid containing stones seems to depend mainly on climatic factors, being higher in countries with desert or tropical climates. Dietary patterns can also lead to an increase in the frequency of uric acid containing stones in association with high obesity rates. Struvite stones are decreasing in most countries due to improved health conditions.

Study on Uroliths Composition in Tertiary Care Hospital of Pakistan

Background: Identification of risk factors for urolith stones formed in the urinary tract could help in preventing the recurrence. Urolith stones analysis utilized modern technology which is unfortunately not done in Pakistan on a routine basis. Development of renal failure may occur due to complications and urinary tract affected by uroliths. Objective: The current study aims to determine the composition of urolith stones seen in patients admitted in single Centre in Pakistan. Materials and Methods: This cross-sectional study was carried out on urolithstones composition surgically removed through minimum access procedure at Urology department of Ayub Teaching Hospital, Abbottabad for period of six months from October 2020 to March 2021. Urinary stones composition was measured through qualitative tests such as infrared and crystallography spectroscopy. Statistical analysis was performed in SPSS version 20. Results: A total of 82 patients with mean age ± SD 45.3±11.7 years having urinary stones were investigated in this cross-sectional study. Male to female ratio was 1.9:1. Male patients (54) (65.85%) were dominant over females (28) (34.15%) in term of stones removal. A high occurrence for urinary stones was bladder or upper urinary tract (81.6%) irrespective of their gender. Calcium containing stones were predominant in ureter, urethra and renal followed by struvite stones (56.8%). Two-third stones in struvite stones were in lower tract while uric acid, calcium phosphates and calcium oxalate were found in upper tract. Calcium oxalate account for 92.60% with mixed composition stones. Conclusion: Our study concluded that the majority of uroliths constitute calcium oxalate or phosphates and struvite stones in our setting. Uroliths formation is caused by urinary tract infection as indicated in our study. Calcium oxalate was the most common among these stones. Struvite stones were the least common one. The prevalence of stones was dominant in male patients compared to female patients. The anatomical location for calcium oxalate and struvite stones was lower tract and bladder respectively. Keywords: Uroliths, Composition, Calcium oxalate, Struvite stone

Kidney Stone Composition in Various Country Around the World

To compare urinary stone composition patterns in different populations around the world in relation to the structure of their population, dietary habits, and climate. 1204 adult patients with urolithiasis and stone analysis was included . International websites were searched to obtain data. We observed 710(59%) patients with calcium oxalate, 31(1%) calcium phosphate, 161(13%) mixed calcium oxalate/calcium phosphate, 15(1%) carbapatite, 110(9%) uric acid, 7(<1%) urate, 100(9%) mixed uric acid/ calcium oxalate, 56(5%) struvite and 14(1%) cystine stones. Calcium stones were the most common in all countries (up to 91%) with the highest rates in Canada and China. Oxalate stones were more common than phosphate or mixed phosphate/oxalate stones except Egypt and India. The rate of uric acid stones, being higher in Egypt, India, Pakistan, Iraq, Poland, and Bulgaria. Struvite stones occurred in less than 5% except India (23%) and Pakistan (16%). Cystine stones occurred in 1%. The frequency of different types of urinary stones varies from country to country. Calcium stones are prevalent in all countries. Uric acid stones seems to depend mainly on climatic factors, being higher in countries with desert or tropical climates. Dietary patterns can also lead to an increase it. Struvite stones are decreasing in most countries.

Metabolic assessment in pure struvite stones formers: is it necessary?

Background and objective: Magnesium ammonium phosphate stones (MAP), also known as struvite stones, are associated with urinary infection and impairment of renal unit. The aim of this study is to evaluate the urinary metabolic risk factors for recurrence of renal calculi in patients submitted to nephrectomy due to MAP stones. Methods: We retrospectively reviewed the charts of patients > 18 years old submitted to total nephrectomy due to pure MAP stones and pure calcium oxalate (CaOx) stones from July 2006 to July 2016. Urinary metabolic parameters were assessed through 24-hour urine exams ≥ 3 months after nephrectomy. Urinary metabolic parameters and new event related to lithiasis were compared. Results: Twenty-eight and 39 patients were included in MAP and CaOx group, respectively. Abnormalities in 24-hour urine samples were similar between groups. Hypercalciuria occurred in 7.1 and 10.3% of patients in MAP and CaOx group, respectively (p = 0.66), whereas hypocitraturia was present in 65.2 and 59.0% of patients with MAP and CaOx group, respectively (p = 0.41). No significant difference in new events was found between MAP and CaOx groups (17.9 vs. 23.1%, respectively; p = 0.60). Conclusion: A 24-hour urine evaluation should be offered to patients submitted to nephrectomy due to pure MAP stones in order to detect metabolic risk, improve treatment, and prevent stone recurrence.

In Vivo Entombment of Bacteria and Fungi during Calcium Oxalate, Brushite and Struvite Urolithiasis

Background: Human kidney stones form via repeated events of mineral precipitation, partial dissolution and reprecipitation, which are directly analogous to similar processes in other natural and man-made environments where resident microbiomes strongly influence biomineralization. High-resolution microscopy and high-fidelity metagenomic (microscopy-to-omics) analyses, applicable to all forms of biomineralization, have been applied to assemble definitive evidence of in vivo microbiome entombment during urolithiasis. Methods: Stone fragments were collected from a randomly chosen cohort of 20 patients using standard percutaneous nephrolithotomy (PCNL). Fourier transform infrared (FTIR) spectroscopy indicated that 18 of these patients were calcium oxalate (CaOx) stone formers, while one patient each formed brushite and struvite stones. This apportionment is consistent with global stone mineralogy distributions. Stone fragments from 7 of these 20 patients (5 CaOx, 1 brushite and 1 struvite) were thin sectioned and analyzed using brightfield (BF), polarization (POL), confocal, superresolution autofluorescence (SRAF) and Raman techniques. DNA from remaining fragments, grouped according to each of the 20 patients, were analyzed with amplicon sequencing of 16S rRNA gene sequences (V1-V3, V3-V5) and internal transcribed spacer (ITS1, ITS2) regions. Results: Bulk entombed DNA was sequenced from stone fragments in 11 of the 18 CaOx patients, as well as the brushite and struvite patients. These analyses confirmed the presence of an entombed low-diversity community of bacteria and fungi, including Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, and Aspergillus niger. Bacterial cells ~1 µm in diameter were also optically observed to be entombed and well-preserved in amorphous hydroxyapatite spherules and fans of needle-like crystals of brushite and struvite. Conclusions: These results indicate a microbiome is entombed during in vivo CaOx stone formation. Similar processes are implied for brushite and struvite stones. This evidence lays the groundwork for future in vitro and in vivo experimentation to determine how the microbiome may actively and/or passively influence kidney stone biomineralization.

Influence of socioeconomic disparities, temperature and humidity in kidney stone composition

Introduction: Large variations in demographic, economic and environmental factors might influence the worldwide distribution of urolithiasis, but scarce data are available concerning their associations with stone composition. We aimed to evaluate the frequency and composition of kidney stones and their associations with temperature, humidity, and human development index (HDI). Materials and Methods: A total of 1,158 stones from distinct patients (47±14 years old, male/female 2:1) were included. The mean annual temperature and relative humidity of each town were considered separately. Results: Calcium oxalate monohydrate (COM) was disclosed in 38.8% of patients, calcium oxalate dihydrate (COD) in 22.1%, mixed COD/apatite in 9.4%, pure apatite in 1.9%, brushite in 1.8%, struvite in 8.3%, pure uric acid in 11.1%, mixed uric acid/COM in 5.6%, and cystine/rare types in 0.8%. Mean HDI of all pooled cities was 0.780±0.03. However, people living in HDI<0.800 regions had twice the odds of having a struvite stone versus those living in HDI>0.800 (OR=2.14, 95% CI 1.11-4.11). Furthermore, a progressive increase in the struvite stones frequency from 4.5 to 22.8% was detected from HDI>0.800 through HDI<0.700. No significant difference for other stone types was disclosed. Separate logistic regression models assessed the association of each stone composition with gender, temperature, humidity and HDI as covariates. Conclusion: Patients living in low HDI areas are more prone to develop struvite stones, possibly due to lower access to healthcare. Temperature and humidity did not represent a specific risk factor for any stone type in the present sample.

Urethral obstruction and urolithiasis associated with patent urachus in a 12-week-old kitten

Case summary A 12-week-old intact male domestic shorthair kitten presented for dysuria. The patient had a urethral obstruction that was relieved with urinary catheter placement. A cutaneous opening at the umbilicus was identified. Three-view abdominal radiographs and a contrast study revealed a patent urachus with no evidence of urine leakage into the abdomen. An exploratory laparotomy was performed that confirmed a patent urachus, which was excised, and cystic and urethral calculi, which were removed via cystotomy. The patient recovered well from surgery, with a 12 h period of stranguria occurring 2 days postoperatively, attributed to residual inflammation. Calculi analysis revealed struvite stones, likely secondary to infection and inflammation. At the time of writing, 3 months postoperatively, the kitten had one episode of hematuria and inappropriate urination, which resolved with a short course of non-steroidal anti-inflammatory drugs, but had been otherwise been asymptomatic and healthy. Relevance and novel information To our knowledge, this is the first report of urolithiasis and patent urachus in a pediatric feline patient. Based on the occurrence of struvite stones in the presence of a patent urachus in an animal of this age, we suspect that chronic infection and inflammation led to the development of urolithiasis. Correction of the patent urachus resulted in almost complete resolution of clinical signs and no crystal formation was appreciated on recheck urinalysis.