Chapter 65 - Kidneys and Ureters Flashcards
What are the primary components of the equine urinary system?
Paired kidneys, ureters, bladder, and urethra.
Where are the kidneys located in the horse?
In the retroperitoneal space.
How much does the left kidney weigh in an adult horse?
800 to 1000 g.
What anatomical feature makes the right kidney less accessible during rectal palpation?
Its cranial position and embedding in the liver.
Describe the shape of the left kidney in horses.
Elongated, resembling a U or inverted J.
How does the blood supply reach the kidneys?
Via one or more renal arteries branching from the aorta.
What are accessory renal arteries, and where do they typically arise?
Additional arteries that may arise from the caudal mesenteric, testicular, ovarian, or deep circumflex iliac arteries.
What characterizes the surface of each kidney?
It is covered by a fibrous capsule.
What is found within the renal cortex of equine kidneys?
Renal corpuscles or glomeruli within Bowman capsules.
How does the corticomedullary junction in horses differ from that in other species?
It is less distinct and typically a deep red color.
What anatomical structure defines the renal columns?
Cortical projections that surround the convex base of renal pyramids.
How many lobes are typically found in equine kidneys?
40 to 60 lobes.
What is the significance of the renal pyramids in horses?
They are largely fused, with some separation at the apices by connective tissue.
What is the structure and function of the renal pelvis?
A funnel-shaped structure that collects urine before it enters the ureter, consisting of three layers.
What are the layers of the renal pelvis?
An external fibrous coat, an intermediate smooth muscle layer, and an innermost layer of transitional epithelium.
What are terminal recesses in equine kidneys?
Narrow tubular structures that extend into the poles of the kidneys, connecting to the renal pelvis.
What role does the renal crest play in the kidney?
It is a fusion of the apices of many pyramids and aids in directing urine flow into the renal pelvis.
How do the ureters prevent vesicoureteral reflux?
The intramural segment of the ureters functions as a one-way valve.
What is the diameter range of ureters in horses?
6 to 8 mm
How long are the ureters in horses?
Approximately 70 cm
What observable phenomenon occurs during cystoscopy in horses?
Streams of urine intermittently exiting each ureter.
What histological components make up the nephron?
Renal corpuscle, proximal tubule, intermediate tubule (loop of Henle), distal convoluted tubule, connecting tubule, and collecting ducts.
How many glomeruli are found in the equine left kidney?
Approximately 10 million.
What histological feature of equine nephrons is larger compared to other species?
The diameter and epithelial height of the collecting duct segments.
What autonomic nerve types primarily innervate the kidneys?
Predominantly sympathetic nerves.
What is the effect of low-frequency stimulation of renal nerves?
Increases proximal tubular sodium reabsorption and renin release.
How does dopamine affect renal blood flow?
Activation of DA-1 receptors increases perfusion of the outer renal medulla.
What unintended effect can occur from administering α2-agonists like xylazine?
Induction of diuresis.
What role does autonomic innervation play in ureteral function?
It regulates ureteral peristalsis.
What adrenergic receptors are found in equine ureteral smooth muscle?
Both α1- and β2-adrenoceptors.
What is the functional role of α1-adrenoceptors in the ureters?
Induce contraction of ureteral smooth muscle.
What happens in the renal pelvis that initiates ureteral peristalsis?
Pacemaker activity.
What unique characteristic is associated with the density of adrenergic neurons in the ureters?
Greater densities in the proximal and intravesicular portions.
What is the primary function of the collecting ducts in the kidney?
To transport urine from nephrons to the renal pelvis.
What are the implications of histologic differences in equine kidneys compared to other mammals?
Potential functional differences that have yet to be investigated.
α1- and β2-adrenoceptors, which induce
contraction and relaxation,
The equine ureteral smooth muscle contains both α1- and β2-adrenoceptors are activated by
norepinephrine
Figure 65-2. Endoscopic image of a left ectopic ureter (LEU) opening into the urethral wall (U) of a filly. (From Cokelaere SM, Martens A, Vanschandevijl K, et al. Hand-assisted laparoscopic nephrectomy after initial ureterocystostomy in a Shire filly with left ureteral ectopia
Figure 65-3. (A) Ventrodorsal radiographic view of a retrograde contrast-enhanced urethrocystogram in a colt with bilateral ectopic ureters showing the bladder (a), pelvic urethra (b), and coxofemoral joint (c). The lower straight white arrow indicates a catheter within the penile urethra and the uppermost white arrows indicate the ureters. (
Figure 65-3. (A) Ventrodorsal radiographic view of a retrograde contrast-enhanced urethrocystogram in a colt with bilateral ectopic ureters showing the bladder (a), pelvic urethra (b), and coxofemoral joint (c). The lower straight white arrow indicates a catheter within the penile urethra and the uppermost white arrows indicate the ureters. (B) Ventrodorsal radiographic view of a percutaneous ultrasound-guided pyelogram in a filly with a left ectopic ureter detailing both hydronephrosis and a markedly enlarged and tortuous ureter. Although both approaches provide greater contrast detail than intravenous pyelography, insertion of the distal ends of the ectopic ureters is not well detailed in either study. (A, From Modransky PD, Wagner PC, Robinette JD, et al. Surgical correction of bilateral ectopic ureters in two foals. Vet Surg 1983;12:141. B, From Tomlinson JE, Farnsworth K, Sage AM, et al. Percutaneous ultrasound-guided pyelography aided diagnosis of ectopic ureter and hydronephrosis in a 3-week-old filly. Vet Radiol Ultrasound 2001;42:349, with permission.)
Figure 65-4. (A) Kidney and ureter removed from a Standardbred colt with a proximal ureteral defect (or tear) through which a probe is inserted.
Figure 65-4. (A) Kidney and ureter removed from a Standardbred colt with a proximal ureteral defect (or tear) through which a probe is inserted. (B) Thoracic wall from the same foal showing a series of five fractured ribs, providing support that ureteral defects in foals can be acquired secondary to trauma.
Figure 65-5. Ultrasonographic images of the right kidney of a horse with renal adenocarcinoma.
(A) Little evidence of normal renal architecture remains. (B) Multiple areas of hypoechoic fluid are apparent within the kidney.
What are the two main categories of disorders that may require surgery in the equine urinary system?
Congenital anomalies and acquired disorders.
List the congenital anomalies that can be found in the equine urinary tract
ectopic ureter
ureteral defects or tears (ureterorrhexis)
vascular anomalies
What is the most common congenital anomaly of the equine urinary tract?
Ectopic ureter.
What happens when the ureteric bud fails to incorporate into the urogenital sinus?
Ectopic ureters open near the urethral papilla in females or in the pelvic urethra in males.
How can ectopic ureters present clinically in foals?
Urinary incontinence, often noticed as scalding of the hind limbs.
What is a significant complication of unilateral ectopic ureters?
The foal may urinate normally if the other ureter is functioning.
Which imaging technique is preferred for locating ectopic ureter openings?
Endoscopy.
Why might intravenous contrast excretory urography be inconclusive in diagnosing ectopic ureters?
Limited detail in visualizing the ureteral course.
What is the surgical treatment for ectopic ureters?
Ureterocystotomy or unilateral nephrectomy.
What preoperative assessments are crucial before surgical intervention for ectopic ureters?
Determining whether the condition is unilateral or bilateral and assessing urinary tract infection status.
What does a successful surgical outcome for ectopic ureter require in terms of bladder function?
Normal detrusor and urethral sphincter function.
What anatomical abnormalities were found in foals with ureteral defects?
Proximal ureteral defects near the kidney.
What clinical signs are associated with ureteral defects or tears?
Decreased nursing, lethargy, abdominal distention, diarrhea, and muscle twitching.
How can ultrasonography assist in diagnosing ureteral defects?
it can reveal dilation of the renal pelvis and affected ureter, as well as fluid accumulation.
What is the recommended imaging procedure when a ureteral defect is suspected?
CT imaging after intravenous contrast administration.
What common complication may arise post-surgery in foals with ureteral defects?
Ascending urinary tract infection (UTI).
What rare vascular anomalies may affect the equine urinary tract?
Renal arteriovenous malformations
distal aortic aneurysms.
What is a potential consequence of renal vascular malformations in horses?
Hematuria or hemoglobinuria.
Which breed of horses is mentioned as being at greater risk for ectopic ureters?
Quarter Horses and Standardbreds.
What complication can arise from ureteral tears following blunt trauma?
Retroperitoneal accumulation of urine or uroperitoneum.
What diagnostic procedure can be used to localize ureteral defects during surgery?
Catheterization of the ureters with methylene blue injection.
What characterizes the anatomical structure of the ectopic ureter?
It may be markedly dilated and tortuous.
How is hematuria evaluated in the context of vascular anomalies?
Ultrasonography, contrast studies, or cystoscopy to determine the source.
What clinical outcomes were reported following nephrectomy in ectopic ureter cases?
Favorable outcomes in most cases, though some complications occurred.
What is the risk associated with a unilateral defect in the presence of hematuria?
Potential fatal exsanguination through the urinary tract.
What anatomical features are typically observed in foals with ureteral defects?
Distended, tortuous ureters and possibly hydronephrosis.
What surgical options exist for treating ureteral defects?
Suturing the defect or nephrectomy.
What is the typical age range for foals presenting with symptoms of ureteral defects?
Symptoms may appear 4–16 days after birth.
What imaging techniques may provide limited information about ectopic ureters?
Intravenous pyelography and traditional contrast studies.
What method is used to assess urinary tract function in horses with ectopic ureters?
Cystometrography.
What anatomical relationship between the ureter and kidney is often compromised in ectopic cases?
The appropriate location and function of the ureteral opening into the bladder.
How can surgical intervention impact long-term function in cases of ectopic ureters?
Persistence of incontinence may occur postoperatively.
What was noted about the sex distribution of ectopic ureter cases in horses?
A predominance of females, likely due to easier recognition of symptoms.
What can complicate the surgical repair of ureteral defects in foals?
The presence of multiple defects and possible renal dysfunction.
What do vascular anomalies in the urinary tract of horses potentially lead to?
Life-threatening hemorrhage requiring urgent surgical intervention.
What complications were noted in cases treated by ureterocystotomy?
Some horses developed postoperative complications leading to death.
What are the typical outcomes following surgical correction of ectopic ureters?
Varying success rates, with nephrectomy showing more favorable results.
Figure 65-6. Resection of the 17th rib permits surgical access for right nephrectomy or nephrotomy procedure.
Figure 65-8. The renal artery, vein, and ureter are ligated with transfixing ligatures before resection and removal of the kidney.
Figure 65-7. All perirenal fat is removed by blunt dissection to permit access to the ureterovascular pedicle.
Figure 65-10. Endoscopic appearance of the ureterovesicular anastomosis demonstrated in Figure 65-9. The ureteral stoma can be observed on the dorsolateral wall of the bladder (arrow).
