¾ Casts may not be found even if proteinuria is heavy
because of dilute urine or because pH is alkaline
¾ In cylindruria, large numbers of casts are seen, but
there may not be any protein in the urine.
Occasional granular cast may be seen.
Granular casts result from the disintegration of the
cellular material of WBCs and epithelial cells into coarse
Never seen in healthy subjects. Seen in terminal diseases
¾ Tubular inflammation and degeneration.
Oval Fat Bodies and Fatty Casts (Fig. 5.30)
Never seen in urines of healthy individuals. In nephrotic
syndrome, fat accumulates in the tubular cells and eventually
sloughs off, forming oval fat bodies. This fat is probably a
cholesterol ester. Fatty casts usually composed of individual
droplets. The presence of fat droplets, oval fat bodies, or fatty
casts is the hallmark of the nephrotic syndrome.
Fatty casts are found in chronic renal disease and indicate
tubular inflammation and degeneration.
Crystals Seen in Normal Acid Urine (Fig. 5.31)
1. Amorphous urates: Yellow-red granules.
2. Uric acid: Yellow or red-brown irregular but usually
whetstone crystals or rhomboids.
3. Calcium oxalate: Refractile, octahedral “envelopes”.
Crystals Seen in Normal Alkaline Urine (Fig. 5.32)
1. Amorphous phosphates: Fine precipitate.
2. Triple phosphate: Colorless, three to six-sided prisms.
3. Ammonium biurate: Yellow brown spheres “thorn
4. Calcium phosphate: Stellate prisms.
5. Calcium carbonate: Colorless spheres or dumb-bells,
Crystals Seen in Abnormal Urine
1. Cystine: Colorless, refractile, hexagonal plate.
2. Tyrosine: Fine needles arranged in sheaves or clumps,
3. Leucine: Yellow, oily appearing spheres with radial
4. Sulfonamide crystals (sulfadiazine): Yellow-brown
asymmetrical, striated sheaves and round forms with
Cholesterol appears as flat notched plates in acid urine,
calcium oxalate and calcium hydrogen phosphate crystals
are found in neutral urine. Uric acid and urates redissolve
on warming at 60oC. Ampicillin is occasionally seen as
masses of long, tiny colorless crystals in acid urine when
Other miscellaneous incidental findings observed on
microscopic examination of urinary sediment are shown
(D) Calcium phosphate; and (E) Ammonium urate crystals in urine
atypical); (F) Starch; (G) Calcium oxalate monohydrate crystals
Bacteria, Fungus and Parasites
Bacteria may or may not (contaminated, overgrown) be
important. A dry film may be made by spreading a drop or
two of the urine sediment on a glass slide, fixed and stained
that more than 100,000 organisms/mL are present, i.e.
Acid-fast bacilli may be seen but urine should always be
cultured as smegma also contains some acid-fast bacilli.
Yeast cells may be seen in UTI (e.g. in diabetes mellitus)
but yeasts are also common contaminants (Fig. 5.34).
These may be seen as fecal or vaginal contaminants.
In Schistosoma haematobium, typical ova may be seen
in urine accompanied by RBCs from urinary bladder.
Trichomonas vaginalis may come from vagina when
urethral or bladder infection is suspected, the protozoa
should be searched for immediately in a wet preparation.
Spermatozoa are generally present in the urine of men
after nocturnal emissions (Fig. 5.35).
¾ Normal people after strenuous exercise
¾ Glomerulonephritis and pyelonephritis.
TABLE 5.7: Common patterns of abnormal urine composition in disease
Color Sp Gr Protein Red cell Casts Microscopic and other findings
Normal 600–2500 Yellow amber 1.003 1.030 0-trace 0 to Occ 0 to Occ Hyaline, casts, must be acid and
Hyperpyrexia Decreased Amber Increased Trace to+ 0 to + None to few Hyaline casts, tubular cells
1–2+ None to + + Hyaline and granular casts
Eclampsia ↓ Amber ↑ 3–4+ None to + 3-4+ Hyaline casts
Diabetic coma ↓ or ↑ Light ↑ + 0 None to + Hyaline casts, glucose, ketonuria
↓ Smoky red ↑ 2–4+ 1–4+ 2–4+ Blood, cellular, granular, hyaline
casts, renal, tubular epithelium
4 + 1–2 + 4+ Granular, waxy, fatty casts,
Very high 4+ O to trace 4+ Hyaline, granular, fatty, waxy
Light to dark Normal or ↓ 1–4+ 1–4+ 1–4+ Blood, cellular, granular, hyaline,
waxy, fatty, broad casts, fatty
Cloudy, dark Normal or ↓ 1–2+ None to+ None to+ Pus casts and hyaline casts.
Normal or ↓ None to+ 0 to trace None to+ Hyaline and granular casts
Light Low, fixed 1–2+ Trace to+ 1–2+ Hyaline and granular casts
Occ = Occasional ↓ = Reduced or decreased ↑ = Increased or raised 0= Nil/Zero
¾ Subacute bacterial endocarditis
¾ Toxicity from heavy metals, salicylates
FIGS 5.35A TO C: (A) Microfilaria; (B) Schistosoma haematobium; (C) Trichomonas vaginalis
Assessment of renal function involves urine analysis; both
routine and microscopic, blood chemistry, urography and
Each kidney contains about 1 million nephrons. A nephron
has a glomerulus and a long tubule that has three parts:
(1) the proximal convoluted tubule (PCT), (2) the thin loop
of Henle (LH), and (3) the distal convoluted tubule (DCT).
The glomeruli are the ultrafilter and the filtrate produced
is like plasma except that it has almost no protein, 180 liters
of this filtrate is produced in 24 hours, of which 178 liters
of water and most of the organic and inorganic solutes are
reabsorbed. Normally, some components of the filtered
solutes are actively absorbed (completely or almost so)—
glucose, phosphate and amino acids, sodium, etc. For some
solutes, such as glucose, phosphate and amino acids, the
maximum reabsorptive capacity of the tubule is limited
and filtered material in excess of this limit is passed on in
the urine. Normal renal threshold for glucose is 180 mg%,
if excess is presented to the nephron, it would result in
glycosuria. Other solutes are not reabsorbed, or are only
passively and partially reabsorbed or are actively secreted by
the tubule. Inulin (a carbohydrate) used for renal function
studies is not at all reabsorbed by the tubules. Some urea is
passively reabsorbed, but most of the filtered urea escapes
reabsorption. Exogenous creatinine, H+
(PSP), iodopyracet (Diodrast), para-aminohippurate and
penicillin are actively secreted by the tubule cells, thus
increasing excretion over the amount filtered.
1. Removal in solution of solid waste substances (e.g.
end products of protein metabolism and foreign
2. Regulation of water balance.
3. Regulation of acid-base equilibrium and electrolyte
excretion. This includes secretion of H+
of ammonia from amino acids, principally glutamine.
The H+ and NH+ produced are exchanged for Na+ 4
in the DCT, thus providing for conservation of this
This has already been dealt in depth in previous chapter
Impaired Renal Function and Blood Chemistry
1. Reduction in glomerular filtration rate or renal blood flow
is accompanied by a rise in blood urea nitrogen (BUN),
creatinine and non-protein nitrogen (NPN). Phosphate
and sulfate retention is common. These days newer
markers like cystatin c are available that reflect kidney
function better than the previously available tools.
2. Low serum protein concentrations occur commonly.
Edema may occur if serum albumin drops below 2.5
gm% or total serum proteins become less than 5.5 gm%.
3. Acid-base equilibrium is disturbed in nephritis.
Renal acidosis is partly due to failure to conserve
sodium during excretion of anions (e.g. chlorides and
4. Anemia accompanies chronic renal disease.
Renal Function and its Evaluation 105 CONCENTRATION: DILUTION TESTS
If the patient’s routine urine specimens contain no sugar
or protein and have a specific gravity of 1.025 or higher, a
concentration test is unnecessary.
Urine specific gravity is a measure of capacity of the
tubules to reabsorb water from glomerular filtrate, thus
concentrating the urine. Determination of osmolality
is better but equipment needed for this is generally not
It is contraindicated in uremia and is unreliable in a case of
1. No fluids for 24 hours after the morning meal (uremic
patients are not to be dehydrated; they may have a
large obligatory renal water loss).
2. Collect urine specimens during the last 12 hours of the
period and determine specific gravity of each.
3. Specific gravity should reach 1.025 or more.
In some patients with edema, nocturnal diuresis will
It is contraindicated in patients with renal/cardiac edema.
The test may be modified for use in the diagnosis of adrenal
1. Evening meal as desired. Nothing orally after 8.00 pm.
2. At 8.00 am empty bladder and drink 1500 mL water
3. Void every half an hour until noon (Save 8 specimens).
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