Thanks to everyone who gave their input. It was good to get such a diverse
(and sometimes contradictory) range of views. Even the vets (and there were
several of them from the same vet practice who examined Toby) couldn't all
agree upon what the problem(s) might be, so I guess I shouldn't feel guilty
about being all confused.

Toby first got ill about 2 months ago - I noticed he had been going to the
litter tray every few minutes - I carted him off to the vet immediately,
where the first vet took a urine sample and tested it for crystals and/or
bacteria. That first test came back positive for bacteria but negative for
crystals. Toby was put on antibiotics, but no change of diet was
recommended (he was being fed IAMS dried and Whiskas Advance wet). He had
an anti-inflammation shot as well, and the frequent litter tray visits
stopped - he got back to his normal routine of 2/3 times of weeing a day.

A few weeks later, when Toby went to the clinic for a follow-up urine test
after completing his course of antibiotics, a second vet discovered that
Toby was badly constipated and had a distended colon. (Toby had always
poo'd every other day - I simply accepted that as his normal routine, I
never suspected he might be constipated. He never showed any signs of
straining or pain when he poo'd before.) After Toby failed to poo for 4
days in a row (despite being treated with both lactulose and cisapride), a
third and fourth vet (from the same clinic) recommended an enema under
anaesthesia - this was duly administered after an x-ray was taken. The last
two vets said the x-ray was inconclusive for a megacolon diagnosis, although
Toby's colon was distended.

Meanwhile, the second urine test came back - Toby had struvite crystals AND
bacteria! Vet no. 2 decided that the bacteria could be lab contamination,
so no additional antibiotics were prescribed. So the decision was made to
put Toby on the Hill's dried w/d and wet r/d combination (both had higher
fibre, are formulated to keep urine urine pH at 6.2 to 6.4, and the wet r/d
would ensure Toby has sufficient fluid intake).

Fast-forward to two weeks later - a third urine test this week showed Toby's
urine is free from either bacteria or struvite crystals. Phew! However,
vet no. 2 felt that it would be wise to continue with the Hill's diet as
well as the lactulose and cisapride treatment for the foreseeable future as
Toby's colon continues to be distended (although he now poos regularly once
every 1 to 1.5 days).

Three different urine tests yielding 3 different results, on top of a
possible idiopathic megacolon diagnosis - the vets don't have a clue why
Toby's constipation developed nor why it progressed to the almost megacolon
stage. It's all pretty much guess-work at this stage - keeping my fingers
crossed that Toby's bowel movements will go back to normal eventually and he
can be safely taken off the cisapride. (Cisapride is expensive and has been
suspected of causing a few human deaths and withdrawn from the human market
so it is not easy to get except thru vets, but lactulose is just a synthetic
sugar and unlikely to cause any long term harm, plus it is much cheaper and
easier to obtain.)

It has been a very stressful couple of months for this daddy!

Devlin
Perth, Australia