Lessons of a traveling internist (Proceedings)

The procedures discussed will include in-hospital urine cultures, voiding urohydropropulsion, and esophageal feeding tube placement.

Urocystoliths

The three most common types of stones seen in dogs and cats are: Magnesium ammonium phosphate (struvite), Calcium oxalate, and Urate.

Magnesium ammonium phosphate (struvite) urocystoliths

Struvite stones are almost always associated with infection in dogs but often sterile in cats. Urine culture is essential.

Urine culture

     1. Equipment necessary:

          a. Sterile inoculating loop (0.001 ml). Disposable plastic loops may be available from your veterinary laboratory or purchased commercially.

          b. Culture plates (blood agar, or ½ blood agar and ½ MacConkey). Available commercially from many sources.

          c. Incubator

     2. Using sterile technique, transfer urine to sterile loop (loop may be gently shaken to remove excess urine)

     3. Streak urine onto culture plate

     4. Incubate culture plate at body temperature (1000F or 370C), plate should be upside down.

     5. Examine plate for growth at 24 hours.

          a. If negative: record results and discard.

          b. If positive:

               i. Determine colony count. With a 0.001 ml loop, 1 colony equals 1,000 colonies/ml; 10 colonies equals 10,000 colonies/ml; 100 colonies equals 100,000 colonies/ml. Record results.

               ii. Send culture plate to lab. Note: some laboratories will not accept culture plates: dab bacteria with sterile culturette and send for antimicrobial sensitivity testing.

               iii. Client invoice states that additional charges will be applied if sensitivity testing is performed (I contact the client when the culture is positive to let them know).

Management of Struvite Urocystoliths:

     1. Surgical removal

     2. Urohydropropulsion: can be performed to push the stone(s) back into the bladder for surgical removal (retrograde) or remove the stones from the body (antegrade).

          a. Technique for retrograde urohydropropulsion (used for urethral stones): the patient is anesthetized and intubated. One assistant occludes the proximal urethra with digital pressure ventrally from the rectum. Saline is infused into the proximal urethra while occluding the tip of the penis. Sterile lubricant may be added to the saline. When the assistant feels the urethra distend, digital pressure is removed and a rush of saline (hopefully including the stone) will be felt entering the bladder. The procedure is repeated until the stone has returned to the bladder.

          b. Technique for antegrade voiding urohydropropulsion (used for removal of urocystoliths): the patient is anesthetized (and frequently intubated). Full relaxation of the urethra is helpful. The patient is held in a vertical orientation allowing all stones to fall into the neck of the bladder. Gentle agitation is performed. The bladder is expressed into a bowl and the sediment examined for the presence of crystals and stones. The urethra can be catheterized and the bladder refilled to allow repeated flushings. Perform repeated radiographs and/or ultrasound examinations to determine completeness of stone removal.

               i. It is reported that stones may be removed up to: male cat: 1 mm (larger if perineal urethrostomy performed), female cat: 5 mm, dogs >20 lbs: 5 mm plus.

               ii. Proceed to surgery if voiding urohydropropulsion fails.

     3. Medical dissolution

          a. Cats (sterile): Hills's S/d (canned or dry), Royal Canin SO formula

               i. Once dissolved, prevent recurrence with Hill's C/d multicare, Eukanuba Urinary S, Purina URst/ox, Royal Canin Urinary SO.

          b. Dogs (usually infected): Hill's S/d diet plus appropriate antibiotic.

               i. Continue antibiotic until 4 weeks after stones have dissolved.

               ii. Monitor for recurrence of infection with scheduled cultures (one week, one month, and 3 months after antibiotic therapy has finished)

               iii. Long term dietary therapy is generally unnecessary for infection-related stones.

Calcium oxalate urolithiasis

Calcium oxalate is now the most commonly diagnosed urocystoliths in cats; almost all feline nephroliths and ureteroliths are composed of calcium oxalate.

Management of Calcium oxalate urocystoliths:

     1. surgery

     2. voiding urohydropropulsion

     3. medical dissolution: not effective.

     4. dietary prevention: increased water intake is very important! Used canned diets.

          a. Dogs: Royal Canin Urinary SO

          b. Cats: Hill's C/d multicare, Eukanuba Urinary O, Purina URst/ox, Royal Canin Urinary SO

Note: recurrence of calcium oxalate urolithiasis is common. I recommend recheck ultrasound every 6 months (initially) with voiding urohydropropulsion if recurrence is detected.

Urate urocystoliths

Urate stones are most often seen in Dalmatians and patients with portosystemic shunts. In any non-Dalmatian breed with urate stones (or ammonium biurate crystals) diagnostics should include evaluation of liver function. Urate stones are frequently radiolucent (not visible on plain radiographs).

Management in Dalmatians:

     1. Surgical: removal is often not necessary unless blockage has occurred. Permanent urethrostomy may be considered but is often not necessary due to the success of medical therapy to prevent recurrence.

     2. Voiding urohydropropulsion

     3. Medical dissolution: Hills U/d diet plus allopurinol are effective for dissolution. However long term treatment with allopurinol is only rarely necessary and may be associated with formation of xanthine stones. Hills U/d diet is also unnecessary for prevention (in most cases) and should be fed long-term only with caution. Try a moderately protein-restricted diet (such as Hill's K/d, Hill's D/d egg dry (plus water), Hill's L/d dry or canned (plus water if dry), Purina NF dry (plus water), or Purina HA dry (plus water).

Anorexia in the cat

Approach to the anorexic cat

It is common for cats to present with poor appetite and weight loss. If the diagnosis cannot be made with routine testing (history, physical examination, CBC, profile, urinalysis, chest XR and abdominal ultrasound) and there is absence of localizing signs (such as vomiting or diarrhea) three main differentials should be considered: intracranial, pancreatic, and gastrointestinal disease.

A careful neurologic and fundic examination should be performed. If the diagnosis remained undetermined the history often helps determine the next course of action: if signs are acute in nature then treatment for pancreatitis is recommended. If signs have been more chronic then biopsies of the gastrointestinal tract and pancreas are recommended, optimally via celiotomy. If biopsies are declined then a trial of prednisone is offered.

Intracranial disease:

The owner may describe behavioral changes, loss of housetraining, or pacing. Neurologic examination may reveal pacing, circling, menace and proprioceptive deficits. Ocular examination may reveal retinal lesions.

Pancreatitis:

Pancreatitis frequently has an acute onset of clinical signs. Most cats present for anorexia, with less than 1/3 showing fever, vomiting, or abdominal pain (Lethargy: 100%, Anorexia: 97%, Dehydration: 92%, Hypothermia: 68%, Vomiting: 35%, Abdominal pain: 25%, Dyspnea: 20%, Diarrhea: 15%).

Laboratory tests:

     1. Serum Amylase: decreases in cats with experimental pancreatitis. In cats with spontaneous pancreatitis, serum amylase activity was not significantly different between cats with pancreatitis and healthy cats.

     2. Serum Lipase: cats with experimentally induced pancreatitis showed significantly increased serum lipase activity, but cats with spontaneous pancreatitis have not. In one study not a single cat with pancreatitis had serum lipase activity outside the reference range.

     3. Serum trypsin-like immunoreactivity (TLI): this measures trypsin and trypsinogen which may leak from an inflamed pancreas. Sensitivity and specificity were initially claimed to be very good, however independent investigation brought the diagnostic value of TLI into question. Azotemia and intestinal disease cause false elevations.

     4. Serum pancreatic lipase immunoreactivity (PLI): A test for lipase of pancreatic origin has been developed and I would describe initial information as "promising." However the true sensitivity and specificity of feline PLI awaits independent review.

Abdominal ultrasound remains my most useful method of diagnosis. The pancreas may appear hypoechoic (dark), enlarged, and surrounded by hyperechoic (bright) areas caused by inflamed peripancreatic fat. Peripancreatic effusion may be present. The reported ultrasonographic sensitivity for the diagnosis of pancreatitis in cats ranges between 11% and 64%. The specificity of these ultrasonographic findings is unknown.

Pancreatic Biopsy is viewed as the most definitive diagnostic tool for pancreatitis, with biopsies collected by celiotomy or laparoscopy. Pancreatic biopsy may be safely performed in cats (!!). Obtain samples from a grossly abnormal area or in the absence of gross changes, from one of the pancreatic tips. Using hemoclips, crush a V-shaped area to obtain the sample. Using suture, crush a protruding area to obtain the sample. Post biopsy complications are rare.

Treatment

Treatment of acute pancreatitis in cats is symptomatic and supportive. Hypovolemia or dehydration is corrected and potassium or glucose supplemented when necessary. Insulin therapy is initiated if hyperglycemia, glucosuria, and ketonuria are present. Antiemetics, such as metoclopramide, dolasetron, maropitant, and/or phenothiazine derivatives may be used. In contradistinction to dogs, enteral feeding of feline patients is recommended. Placement of an esophageal feeding tube is most commonly performed.

Esophageal Feeding Tube Placement (see appendix)

The use of Eukanuba Max Cal or Hill's A/d is recommended for tube feeding. Required intake is calculated as 30 x body weight (kg) + 70 = kcal per day, which should work out closely to the daily fluid requirement. 5 ml of water is flushed into the tube once or twice after recovery from anesthesia. Food is then administered at 5 ml every 4-6 hours on the first day, 10 ml every 4-6 hours the second, and the amount increased gradually until full requirements are reached. Each feeding should be followed with a 5 ml flush of water to clear the tube. Owners should offer food to their pets and continue to tube feed until appetite returns. The length of time is difficult to predict but several owners have tube fed for weeks before their pet regained its appetite.

Cats with pancreatitis generally have a good prognosis. Cats tend to respond quickly to therapy but may be subject to repeated clinical or subclinical attacks of pancreatitis. Most cats that develop pancreatitis survive, even with repeated episodes. The prognosis for cats with acute, severe pancreatitis (patients with severe clinical signs, coagulopathy, and/or low serum ionized calcium) is more guarded.

"Small Cell" Lymphoma of the Intestine.

The most common lymphoma now diagnosed in cats is the "small cell" gastrointestinal form. This disease is seen in FeLV negative older cats and causes weight loss, decreased appetite, vomiting, and/or diarrhea. Gastrointestinal small cell lymphoma is associated with infiltration of small, mature lymphocytes into tissues (rather than large, lymphoblastic cells). The intestines may or may not be palpably thickened; lymph nodes and other abdominal organs may or may not be infiltrated and enlarged. Ultrasonographic changes may be obvious to subtle to absent. Diagnosis of this form of disease relies upon biopsy of an involved organ as fine needle aspiration is often unhelpful. In one study where endoscopy was immediately followed by celiotomy with full thickness biopsies, only 3 of 10 cases of gastrointestinal small cell lymphoma were able to be diagnosed with endoscopic biopsies. This study confirms that endoscopic biopsies may not be diagnostic in all cases.

There have been 3 papers published about the treatment and prognosis for feline gastrointestinal small cell lymphoma. One to two year survival is expected after treatment with prednisone and chlorambucil. The prognosis with prednisone alone has not been reported.

Appendix: esophageal feeding tube placement

Equipment required

     1. General anesthesia (intubation should be performed until the clinician is comfortable performing the procedure; can be performed without intubation after becoming proficient)

     2. Mouth gag

     3. (Non) sterile gloves

     4. Large curved forceps

     5. #15 scalpel blade

     6. Feeding tube (specifically made for esophageal feeding or red rubber; 12-18 Fr)

     7. Needle holders and scissors

     8. Non-absorbable suture material

     9. Bandage material (gauze square, Kling, Vetwrap, white adhesive tape)

Technique

     1. anesthetize patient and place in right lateral recumbency. Generously clip left side of neck and aseptically prepare the area.

     2. Measure feeding tube from proposed entry site to middle of thorax (over heart; where elbow contacts the thorax) and mark tube with permanent marker.

     3. Enlarge holes of feeding tube, if smaller than 14 Fr is used.

     4. Place mouth gag.

     5. Introduce curved hemostat through mouth, into esophagus, with the tips of the forceps pointed up, and press laterally to distend esophagus in the mid cervical region. Note position of external jugular vein.

     6. It is helpful to have an assistant hold the forceps while the surgeon makes a small (several mm) incision over the tip of the forceps. Force the forceps tip through the esophageal wall and skin by incising over the instrument tips.

     7. Open the forceps tips slightly and grasp the distal tip of the feeding tube. Pull the feeding tube out through the mouth.

     8. Using fingers only, curve the feeding tube to reintroduce the tip into the patient's mouth. Push the resulting kink in the tube so that the tube enters the esophagus. This is the difficult part of the procedure.

     9. Adjust length of tube using pre-measured mark.

     10. Secure feeding tube into place using a single Chinese finger-trap suture. A purse string suture around the tube is optional.

     11. A radiograph may be taken to confirm correct tube placement (a single lateral is often sufficient; the tube must not enter the lower esophageal sphincter.

     12. Bandage the site of entry.

References

Evans SE, Bonczynski JJ, Broussard JD, Han E, Baer KE. Comparison of endoscopic and full-thickness biopsy specimens for diagnosis of inflammatory bowel disease and alimentary tract lymphoma in cats. J Am Vet Med Assoc. 2006 Nov 1;229(9):1447-50.

Fondacaro JV, Richter KP, Carpenter JL, et al: Feline gastrointestinal lymphoma:

76 cases (1988–1996). Eur J Comp Gastroenterol 4(2):5–11, 1999.

Hill RC, Van Winkle TJ. Acute necrotizing pancreatitis and acute suppurative pancreatitis in the cat. A retrospective study of 40 cases (1976-1989). J Vet Intern Med. 1993 Jan-Feb;7(1):25-33.

Lulich JP, et al. Voiding urohydropropulsion: lessons from 5 years of experience. Vet Clin North Am Sm Anim Prac 1999 Jan 29:1, 283-292.

Stein TJ, Pellin M, Steinberg H, Chun R. Treatment of feline gastrointestinal small-cell lymphoma with chlorambucil and glucocorticoids. J Am Anim Hosp Assoc 2010;46:413-417