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| Changes which occur with time after collection include: 1) decreased clarity due to crystallization of solutes, 2) rising pH, 3) loss of ketone bodies, 4) loss of bilirubin, 5) dissolution of cells and casts, and 6) overgrowth of contaminating microorganisms. Generally, urinalysis may not reflect the findings of absolutely fresh urine if the sample is over 1 hour old. If the specific gravity is not over 1.022 after a 12 hour period without food or water, renal concentrating ability is impaired and the patient either has generalized renal impairment or nephrogenic diabetes insipidus. Precipitation by heat is a better semiquantitative method, but overall, it is not a highly sensitive test. It can detect albumin, globulins, and Bence-Jones protein at low concentrations. For this reason, most newborn and infant urines are routinely screened for reducing sugars by methods other than glucose oxidase (such as the Clinitest, a modified Benedict's copper reduction test). Example: 5-10 hyaline casts/L casts/LPF. Leukocytes have lobed nuclei and granular cytoplasm. Even with glomerular injury causing increased glomerular permeability to plasma proteins with resulting proteinuria, most matrix or "glue" that cements urinary casts together is Tamm-Horsfall mucoprotein, although albumin and some globulins are also incorporated. When cellular casts remain in the nephron for some time before they are flushed into the bladder urine, the cells may degenerate to become a coarsely granular cast, later a finely granular cast, and ultimately, a waxy cast. Generally, more than 100,000/ml of one organism reflects significant bacteriuria. Crystals: Common crystals seen even in healthy patients include calcium oxalate, triple phosphate crystals and amorphous phosphates. In Egypt, ova from bladder infestations with schistosomiasis may be seen. Early morning collection of the sample before ingestion of any fluid. Clean-catch, midstream urine specimen collected after cleansing the external urethral meatus. A midstream urine is one in which the first half of the bladder urine is discarded and the collection vessel is introduced into the urinary stream to catch the last half. |
| Cystitis, Bacterial bladder Infection Kidney Function That Should Be Checked |