Case1: Three y/o febrile girl has a urinalysis
Many WBC / WBC casts/ 2-3 RBC / many
What is your possible diagnosis?
B) Acute interstitial nephritis
Case 2 : Five y/o girl has a urinalysis report
+3 protein , 10 -15 RBC, 3 - 4 WBC, fatty
casts. No bacteria
What is your possible diagnosis?
B) Nephrotic syndrome
C) Acute interstitial nephritis
Case 3 : Seven y/o boy has a urinalysis
+3 blood , many RBC , many dysmorphic RBC,
RBC casts, WBC cast. No bacteria
What is your possible diagnosis?
B) Renal stone
D) Nephrotic syndrome
• Casts are the only elements found in the
urinary sediment that are unique to the kidney.
• They are formed within the lumens of the distal
convoluted tubules and collecting ducts.
Their shape is representative of the tubular
lumen with parallel sides and somewhat
Examination of the sediment for the detection
of casts is performed using lower power
low-power scanning should be performed along
the edges of the cover slip.
Observation under subdued light is
essential, because the cast matrix has a low
Once detected, casts must be further
identiﬁed as to composition using high-
They are reported as the average number
per 10 lpfs.
CAST COMPOSITION AND FORMATION
• The major constituent of casts is Tamm-
Horsfall protein, a glycoprotein excreted by
the RTE cells of the distal convoluted tubules
and upper collecting ducts.
• Other proteins present in the urinary filtrate,
such as albumin and immunoglobulins, are
also incorporated into the cast matrix.
The rate of excretion of Tamm-Horsfall protein
appears to increase under conditions of stress
and exercise ( transient appearance of hyaline
The protein gels more readily under conditions
of urineﬂow stasis, acidity, and the presence of
sodium and calcium. The extent of protein
glycosylation is also important.
Step-by-step formation of the Tamm-Horsfall
1. Aggregation of Tamm-Horsfall protein into
individual protein ﬁbrils attached to the RTE cells.
2. Interweaving of protein ﬁbrils to form a loose
ﬁbrillar network (urinary constituents may become
enmeshed in the network at this time)
3. Further protein ﬁbril interweaving to form a
4. Possible attachment of urinary constituents to
the solid matrix
5. Detachment of protein ﬁbrils from the
6. Excretion of the cast
• As the cast forms, urinary ﬂow within the
tubule decreases as the lumen becomes
• The accompanying dehydration of the
protein ﬁbrils and internal tension may
account for the wrinkled and convoluted
appearance of older hyaline casts.
The width of the cast depends on the size of
the tubule in which it is formed.
Broad casts may result from tubular
distention or, in the case of extreme urine
stasis, from formation in the collecting ducts.
Formation of casts at the junction of the
ascending loop of Henle and the distal
convoluted tubule may produce structures with a
Any elements present in the tubular ﬁltrate,
including cells, bacteria, granules, pigments,
and crystals, may become embedded in or
attached to the cast matrix.
The most frequently seen cast is the hyaline type,
which consists almost entirely of Tamm-Horsfall
The presence of zero to two hyaline casts per lpf is
the ﬁnding of increased numbers following strenuous
exercise, dehydration, heat exposure, and emotional
stress is normal too.
Pathologically, hyaline casts are increased in
acute glomerulonephritis, pyelonephritis,
chronic renal disease, and congestive heart
Hyaline casts appear colorless in unstained
sediments and have a refractive index similar to
that of urine; they can easily be overlooked if
specimens are not examined under subdued light.
The presence of an occasional adhering cell or
granule may also be observed but does not
change the cast classiﬁcation.
RBC casts is much more speciﬁc, showing
bleeding within the nephron.
RBC casts are primarily associated with
damage to the glomerulus.
RBC casts associated with glomerular damage
are usually associated with proteinuria and
RBC casts have also been observed in healthy
individuls following participation in strenuous
RBC casts are easily detected under low power
by the orange-red color. They are more fragile
than other casts an may exist as fragments.
It is highly improbable that RBC casts will be
present in the absence of free-standing RBCs
and a positive reagent strip test for blood.
The appearance of WBC casts in the urine
signiﬁes infection or inﬂammation within the
They are most frequently associated with
pyelonephritis and are a primary marker for
distinguishing pyelonephritis (upper UTI) from
Most frequently, WBC casts are composed of
neutrophils; therefore, they may appear
granular, multilobed nuclei will be present.
Observation of free WBCs in the sediment is
Bacteria are present in cases of pyelonephritis,
but are not present with acute interstitial
Epithelial Cell Casts
Casts containing RTE cells represent the
presence of advanced tubular destruction.
Similar to RTE cells, they are associated with
heavy metal and chemical or drug-induced
toxicity, viral infections, and allograft rejection.
Owing to the formation of casts in the distal
convoluted tubule, the cells visible on the cast
matrix are the smaller, round, and oval cells.
Bilirubin-stained RTE cells are seen in cases of
Fatty casts are seen in conjunction with oval
fat bodies and free fat droplets in nephrotic
syndrome, but are also seen in toxic tubular
necrosis, diabetes mellitus, and crush
cholesterol demonstrates characteristic
Maltese cross formations under polarized light
and triglycerides and neutral fats stain orange
with fat stains.
Coarsely and ﬁnely granular casts may be of
pathologic or nonpathologic signiﬁcance.
It is not considered necessary to distinguish
between coarsely and ﬁnely granular casts.
The origin of the granules in nonpathologic
conditions appears to be from the lysosomes
excreted by RTE cells during normal
Increased cellular metabolism occurring
during periods of strenuous exercise accounts
for the transient increase of granular casts
that accompany the increased hyaline casts.
Urinary stasis allowing the casts to remain in
the tubules must be present for granules to
result from disintegration of cellular casts.
Waxy casts are representative of extreme
urine stasis, indicating chronic renal failure.
Waxy casts are more easily visualized than
hyaline casts because of their higher refractive
index. As a result of the brittle consistency of
the cast matrix, they often appear fragmented
with jagged ends and have notches in their
Often referred to as renal failure casts, broad
casts like waxy casts represent extreme urine
The presence of broad casts indicates
destruction (widening) of the tubular walls. sts
form in this area and appear broad.
All types of casts may occur in the broad form.
commonly seen broad casts are granular and
Bile-stained broad, waxy casts are seen as the
result of the tubular necrosis caused by viral
The lecturer has no conflict of interests.
Thanks for your attention