Crystalline Obstruction of the Male Feline Urethra John J
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Volume 29 | Issue 3 Article 2 1967 Crystalline Obstruction of the male Feline Urethra John J. Andrews Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/iowastate_veterinarian Part of the Small or Companion Animal Medicine Commons, and the Veterinary Physiology Commons Recommended Citation Andrews, John J. (1967) "Crystalline Obstruction of the male Feline Urethra," Iowa State University Veterinarian: Vol. 29 : Iss. 3 , Article 2. Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol29/iss3/2 This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Iowa State University Veterinarian by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. Crystalline Obstruction of the Male Feline Urethra by John J. Andrews Obstructive urolithiasis, or more cor cent experiments have not supported this rectly phosphocrystalluria (since calculi claim. Likewise, hypovitaminosis A has rarely occur in the feline kidney or ureter), not been supported as a cause by research occurs quite often in the male domestic experiments. cat. The female cat seems to escape this The material which forms the urethral problem because her urethra is wider and obstruction in nearly all the cases of fe more expansible. The male cat, however, line urolithiasis is "struvite" crystal con has a relatively narrow penile urethra and glomerations. Struvite (NH4MgPO,,-6H20 fine urinary crystals may obstruct and -ammonium magnesium phosphate hex pack this urethral canal. If this condition ahydrate) is found in three forms in the is left untreated death is the usual result. feline urinary tract: 1) sabulous or mu Even if treatment is initiated, permanent cus-like plugs of fine struvite crystals urinary tract damage may have already mixed with some cellular debris; 2) "sand" occurred or the condition may reoccur and or granular material of larger struvite plague both the pet owner and the pet for crystals many in small clumps; and the rest of the cat's life. 3) "calculi," larger aglomerations of stru vite crystals up to several millimeters in ETIOLOGY diameter. These can usually be easily The cause of obstructive urolithiasis crushed into smaller ·granules. seems to be any factor that affects the There are two physical-chemical proper urine concentration of phosphate ions, the ties of these crystals that are very impor pH of the urine, the diameter of the ure tant. One, these struvite crystals have a thra or the integrity of the epithelial lining very regular rhomboid shape with perfect of the urethra. Some proposed specific sharp edges. Therefore, the usual feline causes thus include: 1) inadequate fluid calculi is not a smooth rounded stone as intake; 2) infection of the urinary tract, you might find in the dog, but rather it is especially by Proteus or Pseudomonas spp. an irregular conglomeration of regular since these organisms split urea to yield crystals which displays sharp jagged edges ammonia which increases the urine pH; around its circumference. And two, in 3) urinary stasis such as occurs in the nearly ninety percent of the normal fe house-broken cat; 4) castration of the im line urine samples that had a pH reaction mature male; and 5) trauma of the ure above 6.8, struvite crystals were found.8 thral lining. The normal pH of feline urine varies from Too much dietary ash has long been con 6.0 to 7.4; not only in different cats, but sidered to be a cause of urolithiasis but re- also in the same cat at different times. The median urine pH was 6.4. Thus we can • Mr. Andrews is a senior in .the pollege of Veter· Inary Medicine. Iowa State UniversIty. see that the probability of a male cat hav- Issue, No.3, 1967 111 ing struvite crystals in his urine sometime increases the renal tubular secretion is se during his life is quite high. verely reduced. Congestion and engorge ment of the vessels in the bladder wall be CLINICAL SIGNS comes marked as the urinary bladder The usual clinical picture of urethral distends beyond its normal distended size. obstruction is a severely depressed cat that This congestion gives the wall a thickened has been straining for a period of hours to impression upon palpation. The vessels in days. A frequent comment by the owner the renal parenchyma also become con is that the cat appears constipated because gested. Copious amounts of blood and tis he has been sitting in his ''kitty pan" sue debris appear in the urine arising from straining, but no feces have been passed. this engorgement and hemorrhage in the There may also be some vomiting in the renal parenchyma, the degeneration of the severely affected cat. The eyes are usually renal papillae and later from degeneration dull and the mucous membranes may be and hemorrhage in the lower urinary pale to "muddy." Palpation of the abdo tract.3 Blood in the urine is therefore a men will easily reveal a tense thick walled poor prognostic sign. bladder. Unless the cat is very depressed The blood-urea-nitrogen level is in pain may be elicted upon palpation of the creased by the decreased tubular function. abdomen. In many cases the penis is pro Also a certain amount of the retained truded and the penile tip may be a pur urine seeps into surrounding tissues and plish color. is picked up by the capillaries and lym phatics, thus causing the B.U.N. to rise DIAGNOSIS even more. This should be taken into ac The history of straining and the palpa count when the B.U.N. is being used as a tion of the distended bladder are usually prognostic tool. sufficient for a diagnosis. This condition Gross pathological changes include demands immediate treatment and there swollen bluish kidneys, a thickened se fore there is little time to differentiate ob verely congested bladder wall that may ex structive urolithiasis from other condi hibit numerous hemorrhagic areas and tions. presence of "sand" or "calculi" in the blad . Other conditions that might later be der and urethra. considered in differentiation are a stenosis Glycosuria has also been reported due of the urethra or a neoplasm impinging to tubular damage. upon the urethra. A radiograph of the pel vic area might be helpful in differentiating TREATl'l.BNT these conditions, however, crystal obstruc The treatment of fehne urethral block tion is so common this is probably not war age can be divided into three areas: ranted. 1) immediate relief, 2) aftercare, and A blood-urea-nitrogen test could be uti 3) surgical treatment. lized as a prognostic test to determine the amount of kidney damage caused by the IMMEDIATE TREATMENT increased pressures in the urinary tract. Since the diameter of the penile urethra I would like to emphasize that immedi from the prostate caudally is only one-half ate relief of the urinary stasis is more im the diameter of the preprostatic urethra, portant than attempting to confirm the nearly all calculi lodge in the penile por specific diagnosis. Proceed as if it were tion with many lodging within one-half crystalline obstruction and you will be cor inch of the orifice. A parenteral smooth rect in a great majority of the cases. muscle relaxant can be given as soon as a diagnosis has been made. Its usefulness PATHOLOGY is questioned because of the slight amount After crystals have lodged in and ob of smooth muscle surrounding the penile structed the urethra, the intravesicular portion of the feline urethra. lIS Probably pressure begins to rise. As this pressure the only urethral relaxation obtained is in 112 Iowa State University Veterinarian the preprostatic portion where smooth prove to be too traumatic. muscle is more abundant. This may be of Careful flushing should attempt to benefit if back-flushing of the urethra is break down and/or force the obstruction used. back into the bladder. If this proceedure Next a gentle digital manipulation of doesn't succeed a 32g. stainless steel wire the penis should be attempted; lightly roll loop can be used. This can be made by ing the penis between the forefinger and twisting the wire upon itself and leaving a thumb, trying to dislodge or break-up the small loop at one end. This loop is then obstruction. Care must be taken so that inserted into the urethra and a further at further damage to the urethral mucosa is tempt to disintegrate the obstruction is not caused. Even though many of these tried. struvite calculi are quite easily crushed If all else fails, puncture of the bladder many veterinarians choose not to attempt through the abdominal wall should be this manipulation because of the possibil done. This is a "last resort" solution for ity of causing further trauma. If the ob two reasons: 1) it does not solve the pri struction does not dislodge immediately mary problem, the obstruction (although upon digital manipulation (or if you the obstruction may now be easier to back choose not to use it) back-flushing of the flush because of the release of the intra urethra should be attempted. vesicular pressure) and 2) there is a dan Many of these affected cats are so de ger of contaminating the peritoneum with pressed that manipulation and even back pathogenic bacteria leaking through the flushing can be done without an anes needle hole in the urinary bladder wall. A thetic. In fact because the kidneys are one-inch 22g. (or smaller diameter) needle practically non-functional, long acting is the safest size to use. As much urine as barbituate anesthetics or any other anes possible should be withdrawn.