Urine Stone Screen requirements

Transcription

1 Urine Stone Screen requirements Unique Identifying Index Number LP/PA/CB/CBSP030 Version number 4 Issue Date (this version) Document Type Accreditation or Licensing Standard to which this applies Review Interval Author Authorised By (individual or group) Operational UKAS 2 yearly Hazel Borthwick Tim Lang Relevant Staff Groups to which document applies Copy No 1 Medical Laboratory Assistants Biomedical Scientists Clinical Scientists Location of Copies 1. Q-Pulse 2. DMH Reception 3. UHND Reception 4. BAGH Reception Relevant safety data, COSHH and risk assessments: - Mark relevant procedures/policies VDU Lifting/Handling COSHH Spillage Disposal Sharps The above risk/safety assessments must be read and understood before carrying out this procedure. Details are recorded in the main text of the document. CPA Standard CROSS REFERENCES: - CPA Standard. Index No: LPPACBCBSP030 Page 1 of 5 Version no. 3

2 Urine Stone screening requirements Surgery & Diagnostics Care Group Purpose of examination/clinical relevance Renal calculi are formed when the urine is supersaturated with salt and minerals such as calcium oxalate, ammonium magnesium phosphate, uric acid and cystine % of stones contain calcium. They vary considerably in size from small 'gravel-like' stones, to large staghorn calculi. The calculi may stay in the position in which they are formed, or migrate down the urinary tract, producing symptoms along the way. Studies suggest that the initial factor involved in the formation of a stone may be the presence of nanobacteria that form a calcium phosphate shell. The other factor that leads to stone production is the formation of Randall's plaques. Calcium oxalate precipitates form in the basement membrane of the thin loops of Henle; these eventually accumulate in the subepithelial space of the renal papillae, leading to a Randall's plaque and eventually a calculus. 1 Renal stones are common, being present at some time in one in ten of the population, although a significant proportion will remain asymptomatic. The annual incidence is about 1-2 cases of acute renal colic per 1,000 people and the average lifetime risk around 5-10%. Men are more commonly affected than women, with a male to female ratio of 3:1. The difference between the sexes is gradually being eroded. This is thought to be due to lifestyle-associated factors, such as obesity and a Western diet. The peak age for developing stones is between 30 and 50 and recurrence is common. 2 Type of sample 24 hour plain urine bottle no preservative Patient procedure 1. Patient should be given a patient information leaflet PIL/CG/LP/PA/CB/CL01: 24 hour urine collection general. 2. Give the patient one plain 24 hour urine bottle 3. Inform the patient to maintain usual lifestyle and diet during sample collection. 4. Instruct the patient to collect a 24 hour collection into the bottle and refer them to the patient information leaflet. 5. Inform the patient that they must complete their personal details and collection time on the bottle. 6. Inform the patient to bring the sample back to the laboratory or to their GP for courier to the laboratory. For paediatric patients spot collections may be acceptable but refer to the duty biochemist before giving out sample bottles. Procedural steps Samples must be brought to the attention of the laboratory MLA or BMS staff on the day of sample receipt. 1. Check demographics and sample collection times on bottles. 2. Weigh sample to work out the volume. 3. Record the weight on request form and sample. When entering the request onto WinPath the sample volume and times of collection must be put into the clinical details and into the designated WinPath sections. Index No: LPPACBCBSP030 Page 2 of 5 Version no. 3

3 4. Aliquot the following from the 24 hour bottle: a. 5 mls into a plastic tube. b. 15 mls into a plastic tube. 5. Label samples with a LAN and patient demographics 6. Request the following analysis on the corresponding samples: a. ph, 24 hour urate and 24 hour protein and any other tests requested that require a plain sample (such as U&E s) b. 24 hour cysteine 7. Take sample (a) to be analysed on the general chemistry analyser following recording the ph. 8. Sample (b) for cysteine analysis should be stored in the appropriate referred work tray as the sample will be sent to Newcastle RVI for analysis. 9. Adjust the remaining 24 hour sample to ph <3 using 2M hydrochloric acid. IF a paediatric spot sample is received this will have to acidified to ph 1 using the above acid for the assessment of urine oxalate and citrate. 10. Mix the sample well and leave the sample in the cold room until the following morning. 11. Aliquot the following from the 24 hour bottle: a. 5mls into a plastic tube b. 20mls into a white top universal 12. Label the samples with a separate LAN to the samples above (detailed in section 6) and patient demographics 13. Request the following analysis on the corresponding samples: a. 24 hour calcium, magnesium, and phosphate. b. 24 hour oxalate and 24 hour citrate. 14. Take sample (a) to be analysed on the general chemistry analyser 15. Sample (b) should be stored in the freezer prior to referral to UCLH for the oxalate and citrate analysis. If these samples come in on a Friday you must inform the weekend staff that there is a sample requiring processing in the handover book. Quality Control For internal assays (urate, protein, ph, calcium, magnesium and phosphate) refer to the individual SOPs that can be found on Q-Pulse. For the referred work procedure, refer to the SOP on Q-Pulse. Index No: LPPACBCBSP030 Page 3 of 5 Version no. 3

4 Reference ranges 24 hour Calcium mmol/24 hour 24 hour Magnesium mmol/24 hour 24 hour Phosphate mmol/24 hour 24 hour Urate mmol/24 hour 24 hour Protein mmol/24 hour All reference ranges from referral laboratories can be found on the individual reports and are also displayed for the users. Clinical Interpretation If an internal result is outwith the reference interval, the results will be flagged to the user as high and will be held on WinPath for Clinical Biochemist review. All referred results are returned to the laboratory with clinical interpretation as deemed necessary. All referred results are held on WinPath for Clinical Biochemist review. The main types of renal stones are:- Calcium oxalate & phosphate 45% Calcium oxalate 35% Magnesium ammonium phosphate/ calcium phosphate (Struvite) 10% Uric Acid 5% Calcium phosphate 1-3% Cystine 1-2% The main causes of each type of stone are outlined below: Calcium Stones a) Hypercalciuria Hypercalcaemia Hyperparathyroidism Normocalcaemia Malignancy Immobilisation Hyperthyroidism Renal Tubular Acidosis (RTA) Type I b) Hypocitraturia Carbonic Anhydrase Inhibitors, RTA c) Urinary tract infections d) Idiopathic Hyperoxaluria is likely to be involved in the formation of pure calcium oxalate stones. Pure calcium phosphate stones suggest either hypercalciuria or high urinary ph. Hyperuricosuria may contribute to calcium stone formation as can a low urinary citrate which is a recognised inhibitor of calcium stone formation. This is particularly important in Type I RTA where there is already an increased risk of stone formation due to inability to acidify the urine. Oxalate Stones a) Acquired hyperoxaluria e.g. ileal disease b) Primary hyperoxaluria Index No: LPPACBCBSP030 Page 4 of 5 Version no. 3

5 c) Idiopathic Magnesium Ammonia Phosphate Stones (Struvite) a) Urinary tract infections Uric Acid Stones a) Hyperuricaemia e.g. gout, secondary hyperuricaemia. Urinary ph usually subnormal. b) Low urine output. c) Idiopathic. Cystine Stones Cystinuria. References 1. Samuel C.T., Kasides F.P. Biochemical investigations in renal stone formers. Ann Clin Biochem1995;32: Coe F.L., Parks J.H., Asplin J.R. The Pathogenesis and treatment of kidney stones. New Engl J Med 1992;327: Index No: LPPACBCBSP030 Page 5 of 5 Version no. 3