Feline Lower Urinary Tract Disorder (FLUTD) describes a clinical syndrome which manifests as pollakiuria, stranguria, and hematuria. Cats also frequently develop a habit of inappropriate elimination, which can hamper the human-animal bond and may result in relinquishment or euthanasia, making understanding of how to treat this a disorder of crucial importance.
It is estimated that 5% of cats develop FLUTD, with equal representation between males and females. However, due to anatomical differences, there is a greater impact on males as the condition can progress to urinary obstruction, which can be fatal without prompt treatment. Young to middle-aged cats are predominantly affected, while cats over 10 years of age are rarely affected by FLUTD. Older cats with FLUTD symptoms are significantly more likely to be affected by urinary infections, urolithiasis, and neoplasia.
Cats with FLUTD produce inadequate mucosal glycosaminoglycans within the bladder resulting in increased bladder mucosal permeability. Alterations of the autonomic stimulation of the bladder may also contribute to the development of FLUTD. Increased environmental stress has been correlated with the development of FLUTD, likely as a result of the impact of excitatory neural pathways to the bladder and increased production of catecholamines. Clinically this manifest as crystalluria, urolithiasis, urethral spasm, and mucosal plug development.
While there are many causes of FLUTD, it has been reported that more than half of cats have idiopathic disease, while others have crystalluria and mucosal plugs. Notably, only 1-3% of cats with FLUTD have urinary tract infections as a cause of their symptoms. However, rates of urinary tract infection may be as high as 15% in cats over the age of 10 or with concurrent diseases such as diabetes mellitus, hyperthyroidism, and chronic kidney disease. Given the low incidence of infection and growing concerns regarding antibiotic resistance, antibiotics should be used sparingly.
Due to the impact of environmental stressors, a thorough and directed history is vital in addressing underlying factors. Historical information of value includes environment, diet, behavior, water intake, litter box conditions, and hygiene. Development of a standardized form to collect this information while owners are waiting can be helpful in ensuring all pertinent information is acquired, even during an emergency visit.
Progression to urethral obstruction (UO) is the most significant consequence of FLUTD as it can be fatal. Prompt identification of urethral obstruction is vital. Bladder palpation should be performed as a part of the triage exam for all male cats, even those presenting for non-urinary symptoms, as clients may be unaware of changes in urinary habits. Urethral obstruction will cause dehydration, post-renal azotemia, and hyperkalemia. Hyperkalemia can be fatal as it inhibits normal cardiac conductance, leading to arrhythmias ranging from first-degree atrioventricular block to ventricular tachycardia.
A complete blood count, chemistry panel, and urinalysis should be performed on all cats with urinary obstruction. Severe anemia has been reported as a consequence of severe hematuria and is a negative prognostic indicator. The presence of a leukocytosis (>25,000) or leukopenia (<5000) should increase concern for infection and prompt submission of a urine culture and antibiotic administration.
Baseline renal values and electrolytes should be obtained on admission and rechecked prior to discharge. If hyperkalemia is present, electrolytes should be rechecked in 2-6 hours to ensure resolution. Renal values should be rechecked in 24-48 hours. If persistent azotemia is present, continued monitoring is recommended as this could be an indicatory of inadequate fluid therapy, acute kidney injury, or underlying chronic kidney disease.
Urinalysis can be helpful in determining if crystalluria is a component of the disease. If struvite crystalluria or a basic pH is present, specific therapy to acidify the urine will be essential in preventing recurrence. Given the low incidence of infection, urine cultures are not routinely recommended, but should be considered in patients >10 years old or those with concurrent illness such as diabetes mellitus, cystoliths, and chronic kidney disease. Additionally, if pyuria, bacteriuria, leukocytosis, leukopenia, or fever are present, submission of a urine culture is advised.
Immediate stabilization with an IV fluid bolus (20 ml/kg) and analgesics are recommended. If hyperkalemia is present, or suspected based on bradycardia, treatment to reduce the potassium is essential.
There are three approaches to treatment of hyperkalemia; shifting potassium into cells, increasing renal excretion of potassium, and prevention of cardiac conductance abnormalities.
Once stabilized, passage of a urinary catheter to relieve the obstruction is necessary. While heavy sedation is generally necessary, some cats may be too ill to tolerate sedation. In these cases, unblocking can be attempted following administration of an analgesic, such as buprenorphine. All cats should be pre-oxygenated for five minutes prior to the procedure and flow-by oxygen should be administer while sedated. In an attempt to prevent infection, an area around the prepuce should be clipped and aseptically prepared; sterile technique should be used for the procedure. Numerous sedation protocols are appropriate but cardiovascularly sparing drugs are ideal due to the impaired state of the heart if hyperkalemia is present. For longer procedures, inhalant anesthesia may be necessary. Recently a coccygeal epidural technique has been advocated as it decreases the need for systemic sedation and provides superior urethral relaxation, while being easy to perform and inexpensive.
Unblocking can be performed with a variety of different catheter types, but soft and biologically inert materials are preferred (MILA, Slippery Sam, red rubber, etc). Polypropelene (“tom cat”) catheters are effective for difficult obstructions but should be used cautiously as they are associated with increased urethral trauma and are not appropriate as indwelling catheters. Once placed, the catheter should be secured with suture and attached to a closed collection set. Commercially available collection sets are available, though an IV line and an empty sterile fluid bag are equally effective. The catheter should be left in place until the azotemia has resolved, the patient is hydrated, and the urine is clear of debris and blood, typically for 36-72 hours. In a 2016 study, cats with discolored urine at the time of discharge were more likely to suffer recurrence, therefore it is better to err on the side of caution and leave catheters in place until these criteria are clearly met.
Aggressive IV fluid therapy is often necessary, especially in patients with severe azotemia and electrolyte derangements. Once the obstruction has been relieved, the clearance of excess volume and solutes creates an osmotic diuresis resulting in the notorious “post-obstructive diuresis”. A post-obstructive diuresis is defined as urine production in excess of 2ml/kg/hr following relief of an obstruction, but it should be noted that urine output can increase up to 10-fold in severe cases, leading to substantial fluid losses. If adequate fluid therapy is not administered to account for this loss, dehydration will occur. Quantification of urine output can help guide fluid therapy once the cat is rehydrated. Serial patient weights are also immensely helpful in assessing rehydration during hospitalization.
Analgesia should be continued as long as the catheter is in place and for 3-5 days after removal. Anti-spasmodics may be effective in relaxing the urethral smooth muscle. Prazosin, phenoxybenzamine, and acepromazine are the most commonly used medications. Hypotension is a risk of any anti-spasmodic, thus administration should be delayed until the patient is stabilized and normotensive. Retrospective studies have suggested that prazosin is superior to phenoxybenzamine, but no difference in recurrence of obstruction were present in a recent double-blinded study. There has also not been any proven benefit of using NSAIDs; considering their nephrotoxic potential, they should be avoided.
Alternative treatment techniques have been reported including temporary catheterization to relieve the obstruction and decompressive cystocentesis. Temporary catheterization is associated with 30% recurrence within 24 hours. If financial limitations restrict hospitalization and indwelling catheter placement, this is a viable alternative, but should not be used as first-line therapy. Decompressive cystocentesis accompanied with sedation and analgesia is another alternative but is only appropriate for patients with early obstructions that are stable on presentation. Seventy-three percent of stable cats with UO regained the ability to urinate within 72 hours with this approach.
For patients that present with signs of FLUTD but do not have a urinary obstruction, outpatient treatment with anti-spasmodics and analgesics is recommended. Urinalysis is recommended; however, it is often challenging due to the small size of the bladder at presentation. If not possible, clients should be instructed on how to obtain a sample at home for evaluation. If patients are having recurring episodes, implementation of the long-term management strategies listed below should be initiated.
Long-term treatment is multifactorial and involves a holistic approach to medical therapy, diet, and environmental factors.
| Medication | Dose | Proposed Mechanism of Action | Notes |
| Prazosin | 0.25–0.5 mg per cat PO q 12–24 hr for 5 days | Anti-spasmodic, promotes urethral relaxation | Author’s preference |
| Phenoxybenzamine | 0.5 mg/kg PO q 12 hr for 5 days | Anti-spasmodic, promotes urethral relaxation | |
| Acepromazine | 0.25 – 1mg/kg PO q12 | Anti-spasmodic, promotes urethral relaxation | Start at lower doses, increase if needed. Risk of excessive sedation |
| Buprenorphine | 0.01 – 0.03 mg/kg sublingually q8-12 hr | Analgesic | |
| Glycosaminoglycan | Variable depending on product | Decrease mucosal permeability by restoring glycosaminoglycan layer | No clear benefit has been shown with oral supplements or intravesicular infusions |
| Amitriptylline | 2.5 – 12.5 mg per cat PO once daily at night | Decreased incidence of recurrence by decreasing anxiety and stress | Only provides a benefit with long-term use (> 2 weeks) |
| NSAIDS | Robenacoxib Cats <6kg: 6mg PO q24 x 3 days Cats >6kg: 12mg PO q24 x 3 days |
Decrease urinary tract inflammation | No proven benefit, risk of furthering kidney damage |
Generally, the prognosis for survival after UO is very good, however severity of hyperkalemia and presence of anemia are both negative prognostic indicators. The most impactful aspect of this condition is the high incidence of recurrence, which has been reported to be as high as 11% within 24 hours, 24% within one month, and 58% in 6 months.
Prior to initiation of treatment, owners must be counseled regarding the risk of recurrence, as this may be very impactful to their decision-making process. For some, euthanasia is a consideration due to financial and quality-of-life concerns. Though this can be a disheartening decision for a “fixable” condition, we must me empathetic to the stressors this condition inflicts upon both cat and owner. If recurrence of UO occurs following standard treatment, consideration should be given to performing a perineal urethrostomy (PU) to prevent future obstructions.
A general rule-of-thumb is to recommend PU after three episodes of UO, but earlier intervention is reasonable in high-risk cats. Perineal urethrostomy should be decided on carefully, as there is significant risk for recurrent urinary tract infections or urethral stricture, but 88% of owners report their cats had good quality of life following PU.