Andy and the Uroliths


For those of you who like to learn medical terminology, this write-up contains some of our jargon.  I will try to explain it so that this is a learning opportunity as well as an interesting story.  Warning: this page contains graphic description of a surgical procedure.


A 14 year old neutered, male cat (Andy) was presented for a senior work-up, as he had been losing weight.  On physical exam, Andy appeared to be in great condition other than weight loss of 2.5 lbs in 18 months.  As our first steps, lab work was performed including blood chemistries, CBC, and a thyroid level (see bloodwork page for general lab info) and blood pressure was measured.  Because he had a small bladder during the appointment and was too wiggly to obtain urine, it was collected at home and refrigerated overnight until it was brought for analysis.  All the blood values (kidneys, liver, thyroid, glucose, etc.) came back perfectly normal.  The urine (see Urinalysis Page for general urine info) was normal except for the presence of some blood (called hematuria) and 2 different types of crystals.  These 2 types of crystals are generally seen exclusively and not at the same time, so we suspected some of the crystals had developed over the elapsed time between collection and analysis and recommended another urinalysis be performed on a fresh sample.  Because older cats can develop kidney problems (calcification, infection, stones, etc.) and there was blood in the urine, we took some radiographs (x-rays) of his abdomen a few days later.  Andy stayed with us and urinated a few hours later and another urinalysis was immediately performed.


Results of First Urinalysis (UA):


Collection Method: voided

Color:  dark yellow

Appearance:  cloudy

Specific Gravity: 1.055

pH:  7.0

Protein:  3+

Glucose:  Neg

Ketones:  Neg

Bilirubin:  Neg

Occult blood:  3+


RBC/HPF:  3+

Crystals/LPF:  Struvite (magnesium ammonium phosphate) & Oxalate (calcium oxalate dihydrate)

Casts/LPF:  Neg

Epithelial cells/LPF:  Occasional

Bacteria/HPF:  Neg


(For results at The Cat's Meow, a refractometer is used for Specific Gravity; a dipstick is used for the values pH through occult blood; the values reported, "/HPF" or "/LPF" are obtained by looking at the urine sediment under a microscope and are reported as values Per High Power Field or Per Low Power Field -with 0 of each generally considered normal.)




This is a radiograph with Andy lying on his right side (head toward the left of the page).  You can see the spine along the top where it merges into the tail.  On the very right are the pelvis and hind limbs.  On the left, there are a few ribs overlying the liver; to the right of that are the intestines (white with ingesta and black with air/gas).  To the right of that, there are two circles, which are two stones in the urinary bladder.  Notice that they are bright white (like the spine, pelvis, legs, and ribs).  That indicates that the stones are very dense like bone.  The bladder stones are circled.



Results of Second Urinalysis (UA): Obtained soon after X-rays


Collection Method: voided

Color:  dark yellow

Appearance:  clear

Specific Gravity:  1.045

pH:  5.5

Protein:  2+

Glucose:  Neg

Ketones:  Neg

Bilirubin:  Neg

Occult blood:  3+

WBC/HPF:  Occasional

RBC/HPF:  TNTC (too numerous to count)

Crystals/HPF:  None seen

Casts/HPF:  Neg

Epithelial cells/HPF:  Cccasional

Bacteria/HPF:  TNTC (too numerous to count)


Notice how different the pH is in the two samples.  One is acidic and one is alkaline (normal urine pH is 6).  Generally, if urinary stones develop in the body (rather than as "artifact" because of time & refrigeration), struvite stones form in alkaline urine, and oxalate and urate stones form in acidic urine.  Because the second UA was performed within minutes of urination, those results are considered more accurate.  Even though the second UA did not reveal any crystals, the pH would indicate that any stones present would most likely be oxalates or urates.  (Crystals may be seen in the presence or absence of stones, and stones may be seen in the presence or absence of crystals!)  The observation of WBC (White Blood Cells, which are fighter cells that are found in areas of inflammation or infection) and lots of bacteria in a fresh sample also indicate a UTI (urinary tract infection), which is not uncommon in the presence of stones, as the stones can serve as a nidus (nest or breeding place) for infection.


Andy was discharged with antibiotics to begin 48 hours prior to surgery, which was scheduled for a few days later.  Prior to surgery, pain medication was administered.  He was anesthetized and IV fluids were begun.  The surgical procedure consisted of incising the skin and underlying fat, incising through the body wall into the abdomen, opening the urinary bladder (cystotomy), removing the bladder stones, suturing the bladder and filling it with sterile saline to ensure the absence of leakage, and suturing the abdominal wall and skin/subcutaneous tissue.  Andy recovered uneventfully.  Andy was discharged the following afternoon with a new diet (for the prevention of oxalate stones which must be removed surgically vs. the struvite stones which may be dissolved by special diet).  He was to continue the antibiotics for 5 days.

The stones were sent to the lab for analysis. The results tell the composition of both the outside shell and the inside of the stones, which guide our choices of diets and medications for the future.

Urolith analysis revealed that the stones were made of 100% calcium oxalate, inside and outside.  Andy is to continue indefinitely the diet to prevent oxalate stones from forming in the future.  His incision has healed and he is doing well.

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