Feline Constipation – Acute Intervention

(Chronic) constipation is a common problem in (older) cats. In some cases, the underlying cause is easy to identify and resolve, making treatment relatively straightforward. In other cases, however, treatment is more challenging because the cause cannot be fully addressed and/or there is advanced dysfunction of the colon.

In this Vet Info, we will cover the treatment of the acute stage of constipation in cats. In a following Vet Info, we will focus on the chronic management and prevention of constipation.

Definitions

Constipation= irregular or difficult defecation with <3 defecations/week. Chronic constipation = when clinical signs are ongoing for ≥3 weeks.

Obstipation= consequence of chronic constipation. In this case, the constipation is no longer reversible/refractory to treatment.

Megacolon= syndrome with IRREVERSIBLE significant dilation of the colon with reduced motility and elasticity. It is the end stage of colon dysfunction. Megacolon is idiopathic in 2/3 of cases or the result of chronic constipation/obstipation (1/3 of cases).

Medical imaging

On a lateral radiograph of the abdomen, the diameter of the colon can be compared to the length of the 5th lumbar vertebra (L5).

  • Normal = diameter colon/length L5 < 1.3.
  • Megacolon = diameter colon/length L5 > 1.48*. When> 1.62 it is suggestive of a megacolon that is refractory to conservative treatment.

*In acute constipation, diameter colon/length L5 can also be > 1.48. In case of megacolon, this finding is permanent (when in doubt, it is recommended to repeat the radiography).

Treatment of the ACUTE stage

What follows is the treatment of the ACUTE stage of constipation. This is the treatment indicated in the cat at the time it is presented with constipation/obstipation. In some cases (e.g., the cat that is constipated only once and where the underlying cause for the constipation is easily resolved), this treatment is sufficient. However, in the majority of cases, it is important to take additional measures/treatments that prevent it from becoming a recurring problem.

In general:

Every cat with constipation is different and there is no treatment that works for all cats. Therefore, treatment must always be tailored to the individual patient.

Identify and treat underlying causes:

Constipation/obstipation is often the result of an underlying cause. Further diagnostics are recommended to identify possible underlying causes:

  • Thorough medical history: medications that may cause constipation (e.g. calcium channel blockers such as amlodipine, sucralfate, phosphate binders containing aluminum, opioids, etc.)? Type of diet (e.g. fiber content)? Recent dietary changes? Frequency of defecation? Appearance of feces? Home situation (other cats, litter boxes, stress, etc). Other clinical complaints?
  • Physical examination: with special attention to hydration status, abdominal palpation, anal and perianal region, rectal examination (under sedation), neurological examination and orthopedic examination (indications of chronic pain e.g. due to osteoarthritis?).
  • If no obvious cause is found:
    • General blood and urine analysis, including electrolytes (ca, P, K and Na).
    • Total thyroxine in kittens with severe constipation (rule out congenital hypothyroidism) or cats > 7 years suspected of hyperthroidism.
    • Radiography abdomen + pelvis (at least a lateral and a ventrodorsal view): compare diameter of the colon with the length of L5. Old pelvic fracture? Masses or other abnormalities in abdomen? Foreign object in colon? Osteoarthritis?

If an underlying cause is found, it should be treated (if possible): e.g., correction of electrolyte abnormalities, weight loss, analgesia, etc.

Correcting dehydration:

(Chronic) dehydration is an important (secondary) cause of constipation in cats. The majority of cats with constipation/obstipation are dehydrated. Correction of the hydration status is a very important part of the ACUTE treatment of constipation.

Analgesia:

Constipation/obstipation can be very painful. Moreover, (chronic) pain (e.g. due to osteoarthritis) can contribute to constipation/obstipation. Adequate analgesia is therefore always indicated. It is recommended to give drugs that do not further reduce colon motility (e.g., full opioides). Possible options include:

◾ Butorphanol 0.1-0.3 mg/kg IV, IM, SC q 1-4h.

◾ Buprenorphine 10-20 mcg/kg IV, IM, SC q 6-8h.

◾ Metamizole 20-50 mg/kg IV diluted q 8-24h.

Laxatives/prokinetics and rectal suppositories:

Since the most commonly used laxatives are osmotic laxatives that draw fluid to the colon, it is important that the cat is rehydrated first.

TypeProductDose
Emollient (softens the stools)Dioctyl sodium succinate or docusate10-15 ml/cat PO or 5-10 ml/cat via enema
Lubricant (lubricates the stools)Mineral oilBest not orally (risk of aspiration) 5-10 ml/cat via enema
Hyperosmotic (draws extra fluid to the colon)Lactulose0.5 ml/kg PO q 8-12h or 5-10 ml/cat via enema
PEG 3350 (Movicol®,Miralax )*®1.9 g/cat or 1+1/4 teaspoon q 12h (can be doubled if after 48h no defecation is seen) OR can be given via CRI (see later).
Stimulant (stimulates colon motility)Bisacodyl (Dulcolax )®5 mg PO q 24h
Prokinetic (stimulates colon motility in vitro – not demonstrated in vivo)Cisapride2.5 mg/cat PO q 12h
Rectal suppositorySodium laurylsulfoacetate (MicroLax )®2.5-5 ml (half a tube) rectally. May be repeated as needed. Often insufficient with full colon impaction/obstipation

PO = per os (= orally)? CRI = constant rate infusion                                                                                                 * May cause mild, usually not clinical, hyperkalemia with prolonged use. Monitoring of potassium levels is therefore indicated with long-term use.

Enema/ enema:

  • Makes stools moister/softer so they pass more smoothly.
  • Under sedation if necessary.
  • Supplies:
    • 12 Fr (4 mm) red rubber feeding tube.
    • Gloves, waterproof apron.
    • 50-100 ml/kg warm isotonic fluid (alternative = water à small risk of developing hypernatremia).
    • Do NOT use phosphate-containing enema solutions (risk of hyperphosphatemia).
    • Add lubricant to the enema solution.
    • Lactulose (5-10 ml/cat), docusate (5-10 ml/cat) OR mineral oil (5-10 ml/cat) can be added to the enema solution.
  • Techique:
    • Fill syringe and feeding tube with enema fluid.
    • Measure length anus to last rib.
    • Insert prefilled feeding tube into rectum and gently push further (no further than the length you measured from anus to last rib).
    • Inject enema solution SLOWLY (over 2-5 min) to avoid risk of reflex vomiting or colon damage.
    • After injecting the enema solution: wait 15 minutes and keep anus closed.
    • Afterwards, you can try to gently make the stool smaller/softer via palpation of the abdomen.
  • Not effective in about 50% of cats.

Oral PEG 3350 CRI (constant rate infusion):

A good alternative to manual extraction of stool. It saves you time and is much more animal friendly than manual extraction!

  • Place a naso-oesophageal or naso-gastric feeding tube. For placement of feeding tube: see following video: https://youtu.be/w3K9KWJwsqc
  • Use PEG-3350 (Golytely, Colyte, Movicol® , Miralax® ).
  • Dosage: 6-10 ml/kg/hr CRI orally via feeding tube*.
  • Defecation is seen on average within 8 hours (6-14 hours).
  • Average total dose needed = 80 mL/kg
  • Can be combined with an enema.

Manual extraction:

  • After an enema.
  • = the physical removal of impacted feces from the colon or rectum
  • ONLY IF NOTHING ELSE WORKS!!!
  • ALWAYS under general anesthesia + intubation (prevention of aspiration).

Additional treatments:

Some cats need anti-emetics (e.g., maropitant 1 mg/kg IV, SC or PO), appetite stimulant medications (e.g., mirtazapine transdermal or 1/4 tablet of 7.5 mg or 1/8 tablet of 15 mg orally every other day or capromorelin 2 mg/kg PO q 24h), nutritional support, etc.

IV = intravenous/SC = subcutaneous/PO = orally

References

  • Trevail T et al. Radiographic diameter of the colon in normal and constipated cats and in cats with megacolon. Vet Radiol Ultrasound 2011 Sep-Oct;52(5):516-20
  • Garr AP, Gaunt MC. Constipation resolution with administration of polyethylene-glycol solution in cats. J Vet Intern Med. 2010; 24:723 [abstract] 

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