Urology

What are the three key areas of focus regarding the pathophysiology of urolithiasis?

Understanding the principles of calculi formation, awareness of relative prevalence of stone types, and describing key features of the common types of uroliths and their differences.

What are the three key areas of focus regarding the diagnosis and management of urolithiasis?

Recognizing cases, describing multiple techniques for removing calculi from the urinary bladder, and recommending strategies to prevent recurrence.

Besides recognition of cases and removal techniques, what is another key area of focus regarding the diagnosis and management of urolithiasis?

Recommending strategies to prevent recurrence

What are the two key areas of focus regarding urolithiasis beyond pathophysiology, diagnosis, and management?

Describing the basic steps for treating a patient with an obstructive urethral calculus and understanding options for managing a patient with nephroliths or ureteroliths.

What factors influence the formation of uroliths?

Crystals vs. stones and clinical considerations.

What is the easy answer to 'Why do uroliths form?'?

Mineral components precipitate out of a solution (urine) and aggregate before they can be cleared.

What 3 factors lead to stones?

Nucleation, growth, and aggregation aided by retention.

Besides H2O, what other factors influence precipitation and prevent stone formation?

Solutes, pH, other ions, surfaces, proteins, inhibitors, and bacteria.

Besides minerals, what else are stones comprised of?

A matrix of proteins and GAGs, which can either promote or inhibit crystal growth/aggregation.

What typically causes Struvite, Urate, and Cystine crystal formation?

Increased solute concentration.

Besides increased solute concentration, what else is a cause of Calcium Oxalate (CaOx) crystal formation?

Lack of other ions and inhibitors.

What do crystals indicate?

Supersaturation.

Crystals are not equal to what?

Uroliths and/or pathology.

What are common stone types dependent on?

Dogs vs. cats, prevalence, and trends.

What two types of stones are found in the highest percentage in felines?

Struvite at 52% and Calcium Oxalate at 35%

What are feline plugs mostly comprised of?

Struvite.

What has been the trend regarding canine uroliths over the last 10-15 years?

A similar trend of increasing CaOx in 80s-90s, fairly stable for last 10-15 years, slight decrease in urate/purines, and increase in cystine.

How is the presence of stones suspected?

Based upon the history and physical exam, specifically classic LUTD signs (pollakiuria, strangury, dysuria), palpable pain in caudal abdomen or stones in bladder, or sometimes feeling stones in the urethra on rectal palpation or urinalysis showing active sediment (pyuria, hematuria) and crystalluria.

How are stones diagnosed?

By imaging, including radiographs, ultrasound, contrast studies, and endoscopy.

Besides knowing there are stones, what further information is needed for diagnosis?

Number, size, location, risk factors, and concurrent disease. The definitive diagnosis is stone analysis.

What influences treatment of stones?

Suspected underlying risk factor (e.g. UTI, breed-specific problem), known/suspected stone type, and location.

What is the initial treatment for a life-threatening urethral or bilateral ureteral obstruction?

IV fluids.

What is an additional critical step in the emergency treatment of urethral or bilateral ureteral obstruction?

Relieve the obstruction.

When is medical dissolution a reasonable treatment option?

In some patients with certain stone types (struvite, +/- urate), especially if stones are in the bladder.

What is usually the best treatment option for struvite stones?

Diet to reduce solute concentration and modify urine pH, plus antibiotics if UTI present, and possibly pH modulation medications.

How should a patient respond to medical dissolution of struvite uroliths in dogs in 2-4 weeks?

Compliance - BUN & USG should decrease

If a struvite stone does not decrease with a struvolytic diet, what are the possible causes and what steps should the DVM take?

Inadequate Control of UTI - Administer antimicrobics throughout the entire period of dissolution; Incomplete Dietary Compliance To verify, measure using pH meter; Incorrect or Incomplete Prediction of Mineral Composition Consider minimally invasive or surgical methods to remove uroliths

How is catheter removal of stones performed?

Catheter tip at trigone, patient held upright (bladder neck down), bladder agitated and emptied, then refill and repeat.

What is the size constraint for voiding urohydropropulsion?

All stones smaller than urethral diameter, <5mm in most cases.

What is the process for urohydropropulsion?

General anesthesia, catheter used to fill bladder with saline then removed, hold patient upright, agitate bladder, then express to achieve forceful stream, and collect stones for examination. Repeat until all stones collected.

What can be utilized during cystoscopic retrieval?

Empty sheath, stone baskets, and Ellik evacuator.

What are the two methods for lithotripsy?

Extra-corporeal shockwave (ESWL) and Laser lithotripsy.

What is the primary use for extra-corporeal shockwave (ESWL) lithotripsy?

When uroliths are fixed in location.

What is the most common use for Laser lithotripsy?

Cystic and urethral calculi.

What are the goals of preventative stragies?

Prevent uroliths by reducing risk factors or maximize time before intervention is needed with a monitoring strategy to allow least invasive procedure.

What are some non-specific prevention strategies?

Increase water consumption to decrease mineral concentration in urine and reduce the possibility of supersaturation.

What are the key monitoring parameters?

USG, BUN, urine pH, urine sediment, and imaging.

What are specific prevention strategies based on?

Knowledge of mineral composition and knowledge of individual case (risk factors and disease factors).

What can be done to prevent sterile struvites?

Preventing supersaturation events with diet and monitoring USG and urine pH (add acidifiers only if needed).

What are the typical risk factors for CaOx?

Breed (Min. Schnauzer, Shih Tzu, Lhasa Apso, Yorkies, others…), glucocorticoids, 1° hyperparathyroidism, chronic metabolic acidosis, and obesity.

Which diets are commonly used for CaOx prevention?

Hill’s u/d, Royal Canin S/O, and Hill’s w/d (w/ added citrate).

What are the two potential actions of Potassium Citrate?

pH modulation and correction of hypocitraturia.

How is Cystine prevented/monitored?

↓ protein diet & alkalinization and D-penicillamine, Thiola. M>>F- Neuter!

How is purine/urate prevented/monitored?

↓ purine/protein diet & alkalinization and Allopurinol. Check for liver dysfunction (esp. PSVA)

What causes a hereditary xanthinuria?

Rare autosomal recessive disorder of purine metabolism caused by mutations in xanthine dehydrogenase (Type I) or molybdenum cofactor sulfarase (Type II) genes.

When should a nephrolith be managed?

If it is causing problems: obstruction, infection, or deteriorating renal function. Can try to dissolve struvite.

What are the clinical findings for ureteroliths?

Clinical signs common, not specific, Most obstructed (n=143; 92%), Most azotemic (incl. unilateral), Majority (n=101; 62%) had nephroliths, CaOx predominate (91/93 = 98%), 8% Culture positive.

What are the goals for medical management of ureteroliths?

Stabilize, facilitate passage, and prevent growth.

What is the protocol for medical management of ureteroliths?

Fluids, diuretics, analgesia, and +/- alpha adrenergic antagonists, glucagon, calcium channel blockers…

What are the interventional/surgical options for treating ureteroliths?

Stents, SUBs, and Ureterotomy / Neoureterostomy.

How do SUBs bypass the ureter?

Flow is from the kidney through the shunting port & into the bladder, bypassing the ureter.

What do compound uroliths contain?

Distinct layering of different minerals.

When treating compound uroliths with medical treatment, which layer should you focus on first?

Focus on outer layer mineral.

When preventing compound uroliths, which mineral should you focus on?

Focus on mineral in nidus.

UTI

A common cause of lower urinary tract disease (LUTD) in dogs (14%) but uncommon in cats (1-3%). It isn't synonymous for bladder infection, and may involve kidneys, ureters, bladder, urethra, prostate.

Ascending Infection

The primary route of infection in the urinary tract, requiring adherence and colonization.

Bacterial virulence factors

Motility, adherence, toxin production, iron acquisition, and immune evasion.

Anatomic barriers against UTI

Urethral length, urethral high pressure zone, and urothelium.

Mucosal Barriers against UTI

Glycosaminoglycans, Immunoglobulin production, Cell exfoliation, and Commensal bacteria.

Lower urinary tract clinical signs that could indicate infection

Pollakiuria, Stranguria, Hematuria, Strong odor

Upper urinary tract clinical signs that could indicate infection

Anorexia, lethargy, back pain, PU/PD (chronic)

CBC results to indicate UTI

Normal / “Stress” leukogram or Leukocytosis

Urinalysis components for UTI diagnosis

Bacteria, specific gravity, and casts.

Preferred method for urine collection for culture and sensitivity

Cystocentesis

Imaging techniques to assess UTIs

Radiographs, Ultrasound, and Excretory urogram (EU, IVP)

Sporadic bacterial cystitis (aka “uncomplicated cystitis”)

No predisposing factors found, normal anatomy, no neurological deficits, no immune-suppressive diseases or medications, “Typical” lower UTI clinical signs, and < 3 episodes/year

“Complicated” UTI

Identifiable predisposing factors, Ectopic ureters, Neurologic disease, Hyperadrenocorticism, Neoplasia, and Immune-suppressive medications

Subclinical bacteriuria

Positive culture w/o clinical signs

Recommended duration of antibiotic treatment for uncomplicated (sporadic) bacterial cystitis

3-5 days

Persistence in UTI treatment

Failure to eradicate organisms, demonstrated by positive culture 3-5 days after initiation of antibiotic therapy (same strain)

Relapse in UTI treatment

Positive culture ~5-7 days after discontinuation of antibiotics with same strain

Reinfection in UTI treatment

Culture different organism

Methenamine hippurate

Urinary antiseptic that is converted to formaldehyde and requires acidic urine (pH < 6)

Treating first-time uncomplicated infection

Pick ONE drug (see notes or ISCAID guidelines for bacterial UTI’s – 2019), treat for 3-5 days, and culture if clinical signs persist >3 days, or if rapid recurrence

What is Pigmenturia?

Abnormal amounts of RBCs, hemoglobin, bilirubin, or other pigments in the urine.

What characterizes macroscopic pigmenturia?

Visible discoloration of urine; presenting complaint may include "bloody" or dark urine.

What are the characteristics of microscopic pigmenturia?

No visible discoloration of urine, but >5 RBCs per high-power field on microscopic examination, or a positive "blood" result on dipstick.

What is the primary goal when performing a urinalysis for suspected pigmenturia?

Differentiating intact RBCs from free pigments.

Name some causes of macroscopic hematuria in the upper urinary tract.

Renal neoplasia, trauma, acute bacterial pyelonephritis, calculi.

Name some causes of macroscopic hematuria in the lower urinary tract.

Infection, inflammation, feline idiopathic cystitis (FIC), calculi, neoplasia.

Name some systemic conditions associated with macroscopic hematuria due to hemoglobinuria.

Immune-mediated hemolytic anemia, disseminated intravascular coagulation, transfusion reaction, heat stroke.

What are some potential causes of myoglobinuria?

Severe crush injury, prolonged seizures.

What historical information is important to gather when investigating hematuria?

Dysuria/stranguria, pollakiuria, changes in urine stream, timing of hematuria, reproductive status, drug history.

What are some potential causes of hematuria accompanied by dysuria/stranguria?

Cystitis, urolithiasis, prostatitis, benign prostatic hyperplasia, neoplasia, trauma.

What are some potential causes of hematuria without dysuria?

Renal neoplasia, polycystic kidneys, trauma, nephroliths, pyelonephritis, idiopathic renal bleeding, glomerulonephritis, heat stroke, coagulopathy.

What are the key components of the physical exam when evaluating pigmenturia?

Observe urination, palpate kidneys and bladder, perform rectal and vaginal exams, and examine the prepuce/penis.

What are some key considerations when performing a urinalysis for pigmenturia?

Verify blood vs. pigment, identify iatrogenic hemorrhage, localize the source of bleeding, and check for bacteria, casts, and parasite eggs.

What can be assessed using radiographs in a pigmenturia case?

Assess kidney size and shape, prostate size and shape, and look for uroliths or lymph node abnormalities

What structures are typically evaluated during abdominal ultrasound for pigmenturia, and what specific abnormalities are you looking for?

Kidneys, bladder, and prostate, including FNA of cysts, masses, abscesses, and stones.

What are common causes of hemoglobinuria?

Immune-mediated hemolytic anemia, DIC, heat stroke, Caval syndrome (D. immitis), and other causes of hemolysis.

What are the key initial considerations when approaching a case of pigmenturia?

Blood vs. hemoglobin vs. myoglobin, upper or lower urinary tract signs.

What are the main differentials to consider when pigmenturia is accompanied by pollakiuria and stranguria?

Lower urinary tract disease, including infection, uroliths, neoplasia, and inflammation.

If a free catch urine sample has blood, but cystocentesis does not have blood what does that mean?

Problem is distal to the bladder (urethra, vagina, vestibule).

What are some non-specific clinical signs of Feline Lower Urinary Tract Disease (FLUTD)?

Dysuria, pollakiuria, pain, vocalization, periuria, pigmenturia, and potentially obstruction. Generally no polyuria or polydipsia.

What is Feline Idiopathic Cystitis (FIC)?

Idiopathic cystitis is diagnosed when no underlying cause is identified for FLUTD (Feline Lower Urinary Tract Disease).

What percentage of FLUTD cases are attributed to Feline Idiopathic Cystitis (FIC)?

FIC may account for > 50% of all FLUTD cases.

List some differential diagnoses for FLUTD.

Behavioral problems, FIC, uroliths, UTI, and neoplasia.

What are the typical clinical signs of FIC?

Non-specific signs of lower urinary tract disease and few systemic signs (unless obstructed).

How is FIC diagnosed?

Diagnosis of exclusion, often presumptive based on history, physical exam, and potentially lab work and imaging.

List some risk factors associated with Feline Idiopathic Cystitis (FIC)?

Neutered status, age (approximately 2-7 years), breed, gender (male), dry food diet, overweight condition, environmental factors and stress.