Unusual Pet and Avian Veterinarians Annual Conference 2016 p 1 2 - 1 8 . 1 PERSISTENT REMNANT URACHUS AND VESICOURACHAL DIVERTICULUM IN A GUINEA PIG. Dr Brianna Talbot BScAgr (Hons), BVSc, MANZCVS (Unusual Pets) Dr Hamish Baron BVSc (Hons), MANZCVS (Avian Health) The Avian Reptile and Exotic Pet Hospital The University of Sydney, 415 Werombi Road, Camden, NSW 2570 ABSTRACT A twoyearold female guinea pig (Cavia porcellus) was presented with a six week history of haematuria that was unresponsive to medical therapy. Physical examination revealed an abnormal opening of the urethra and an umbilicus that appeared recessed with a central depression. Ultrasound examination confirmed a persistent urachal ligament with an intraluminal component while a positive contrast urethrocystogram revealed a bladder diverticulum. Surgery was performed to remove the umbilicus and persistent urachal ligament and bladder diverticulum in addition to vulval dermatoplasty to remove the abnormal urethral covering. The guinea pig recovered well and did not have any further episodes of haematuria. INTRODUCTION There have been a variety of urachal anomalies reported in several animal species including horses, calves and cats (LojszczykSzczepaniak et al, 2010, Laverty and Salisbury 2002, Baxter et al, 1987). Many of these are detected perinatally due to clinical signs such as persistent moisture around the umbilicus, fluid leaking from the umbilicus, cystitis or urolithiasis. The urachus is an embryonic structure that functions as a duct connecting the foetal urinary bladder with the allantoic sac, permitting the passage of urinary waste from the bladder to the placenta for removal. After parturition, it undergoes atrophy and the lumen is obliterated and a cicatrix results at the bladder apex. If this process is disturbed and there is a failure of the urachus to completely involute then a number of anomalies can result. Depending on the urachal portion involved in the pathological process, the development of patent urachus, urachal ligament, sinus or cyst and vesicourachal diverticulum can result (LojszczykSzczepaniak et al., 2010). Sexual determination of guinea pigs is fairly straightforward. The sow has a Y shaped anogenital opening with the top branches of Y surrounding the urethral opening. The vulva is located centrally at the intersection of the branches with labia located laterally on both side and the anus is located at the base of the Y (Turner 2013; Hargaden and Singer 2012). The urogenital opening is usually sealed by a vaginal closure membrane (Figure 1), which opens during oestrus and parturition. This report details the case of a young female guinea pig with a congenital persistent urachal remnant and bladder diverticulum (vesicourachal) in addition to an abnormal urethral opening most likely due to labial fusion that was surgically corrected. To the authors’ knowledge, this is the first recorded case of such condition in a guinea pig.
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Unusual Pet and Avian Veterinarians Annual Conference 2016 p 1 2 - 1 8 .
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PERSISTENT REMNANT URACHUS AND VESICOURACHAL DIVERTICULUM IN A GUINEA PIG. Dr Brianna Talbot BScAgr (Hons), BVSc, MANZCVS (Unusual Pets) Dr Hamish Baron BVSc (Hons), MANZCVS (Avian Health) The Avian Reptile and Exotic Pet Hospital The University of Sydney, 415 Werombi Road, Camden, NSW 2570
ABSTRACT
A two-‐year-‐old female guinea pig (Cavia porcellus) was presented with a six week history of haematuria that was unresponsive to medical therapy. Physical examination revealed an abnormal opening of the urethra and an umbilicus that appeared recessed with a central depression. Ultrasound examination confirmed a persistent urachal ligament with an intraluminal component while a positive contrast urethrocystogram revealed a bladder diverticulum. Surgery was performed to remove the umbilicus and persistent urachal ligament and bladder diverticulum in addition to vulval dermatoplasty to remove the abnormal urethral covering. The guinea pig recovered well and did not have any further episodes of haematuria. INTRODUCTION
There have been a variety of urachal anomalies reported in several animal species including horses, calves and cats (Lojszczyk-‐Szczepaniak et al, 2010, Laverty and Salisbury 2002, Baxter et al, 1987). Many of these are detected perinatally due to clinical signs such as persistent moisture around the umbilicus, fluid leaking from the umbilicus, cystitis or urolithiasis.
The urachus is an embryonic structure that functions as a duct connecting the foetal urinary bladder with the allantoic sac, permitting the
passage of urinary waste from the bladder to the placenta for removal. After parturition, it undergoes atrophy and the lumen is obliterated and a cicatrix results at the bladder apex. If this process is disturbed and there is a failure of the urachus to completely involute then a number of anomalies can result. Depending on the urachal portion involved in the pathological process, the development of patent urachus, urachal ligament, sinus or cyst and vesicourachal diverticulum can result (Lojszczyk-‐Szczepaniak et al., 2010).
Sexual determination of guinea pigs is fairly straightforward. The sow has a Y shaped anogenital opening with the top branches of Y surrounding the urethral opening. The vulva is located centrally at the intersection of the branches with labia located laterally on both side and the anus is located at the base of the Y (Turner 2013; Hargaden and Singer 2012). The urogenital opening is usually sealed by a vaginal closure membrane (Figure 1), which opens during oestrus and parturition.
This report details the case of a young female guinea pig with a congenital persistent urachal remnant and bladder diverticulum (vesicourachal) in addition to an abnormal urethral opening most likely due to labial fusion that was surgically corrected. To the authors’ knowledge, this is the first recorded case of such condition in a guinea pig.
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Figure 1: Normal anatomical appearance of the external genitalia of a female guinea pig (Sudow et al., 2011).
CASE REPORT
A two-‐year-‐old female entire guinea pig was referred to the Avian Reptile and Exotic Pet Hospital at Sydney University’s Camden Campus for persistent haematuria that was unresponsive to medical therapy. The guinea pig had been purchased when young and had been housed with another guinea pig that was clinically well. The haematuria had been present for six weeks and had been treated with enrofloxacin and meloxicam with no apparent clinical improvement. The guinea pig remained bright and active during this period and was apparently unaffected by the haematuria.
On physical examination the guinea pig was found to be bright, alert and responsive; it weighed 771 grams and was in ideal body condition based on the PMFA guinea pig body condition score chart (www.PMFA.org.uk). Abdominal palpation did not reveal any abnormalities; the bladder was empty prohibiting urine collection. Grossly the umbilicus was abnormal with the surrounding tissue involuting slightly towards a central wick in the depression. The perineum appeared abnormal with a visible membrane covering the urethral opening (Figure 2). Figure 3 is presented for comparison of anatomy.
Figure 2: Appearance of the perineum of the patient demonstrating the membrane covering the urethral opening. A 24g intravenous catheter is inserted into the urethra to illustrate the thickness of the tissue.
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Figure 3: Normal anatomy of a female guinea pig for comparison (Turner 2013). U: urethral opening; V: vaginal opening and A: anus.
The patient was placed under gaseous anaesthesia using 3% isoflurane (Bayer Australia Pty, Ltd, Gordon, NSW 2072) and oxygen at 1.5L/min and maintained on a face mask while plain digital radiographs were performed. No abnormalities were detected and the bladder was small and obscured by the caecum.
The guinea pig was started on sulfamethoxazole and trimethoprim at 15mg/kg PO BID (Roche Australia Pty Ltd, Dee Why, NSW 2099, Australia) and meloxicam at 0.5mg/kg PO BID (Apex Laboratories Pty Ltd, Somersby, NSW 2250) and the
decision was made to perform an abdominal ultrasound the following day.
An ultrasound of the abdomen was performed and revealed a tubular hypoechoic structure at the level of the mid ventral urinary bladder wall. This structure coursed from the lumen of the urinary bladder ventrocranially to the ventral abdominal wall and passed through the ventral abdominal wall into the umbilicus. Where the tubular hypoechoic structure attached to the urinary bladder wall there was a thin hyperechoic attachment extending distodorsally into the urinary bladder lumen.
Figure 4: Ultrasound examination of the bladder, the ventral urinary bladder attachment extending towards the umbilicus is outlined by the circle
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A retrograde positive contrast urethrocystogram was carried out using iohexol 240 (10ml/kg; GE Healthcare Australia Pty Ltd, NSW 2150 Australia) by inserting a sterile 1.0 x 130mm 3FG feline urinary catheter (DLC Australia Pty Ltd, 17-‐19 Horne Street, Hoppers Crossing Vic 3029 Australia) into the urethra and infusing 3ml of dilute contrast material. Subsequent radiographs confirmed the
presence of a urinary diverticulum. The bladder distended normally with the infusion of the contrast and at the completion of the study; there was a small “V” shape present at the ventral urinary bladder margin.
Figure 5: Retrograde positive contrast urethrocystogram radiograph showing distension of the urinary bladder and the ventral persistent diverticulum marked by arrow.
A final diagnosis of persistent remnant urachus, bladder diverticulum and labial fusion was made.
The guinea pig was taken to surgery to remove the persistent urachal ligament, the bladder diverticulum and for correction of the abnormal urethral tissue. She was premedicated with 0.1mg/kg medetomidine (Troy Laboratories Pty Ltd, Glendenning NSW 2761) and 10mg/kg ketamine (Ceva Animal Health Pty Ltd, Glenorie NSW 2157) and 0.2mg/kg butorphanol (Troy Laboratories Pty Ltd, Glendenning NSW 2761) subcutaneously then induced using isoflurane at 3% and oxygen 1.5L/min via a face mask and maintained on the
same throughout the though procedure with no complications. A 24g intravenous catheter was placed in the left cephalic vein to facilitate intraoperative fluid therapy using compound sodium lactate (Hartmanns solution, Baxter Healthcare Pty Ltd) at 10mg/kg/hr.
The ventral abdomen was surgically prepared and a 4cm midline incision was made 1cm proximal to the umbilicus and extended caudally to towards the pubis. The linea alba was moderately thickened surrounding the umbilicus. With the incision extended caudally the urachal stalk was located and confirmed to be attached to the bladder. The
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umbilicus and urachal stalk were then excised and dissected down to the bladder; it was then crushed and ligated with a fine monofilament suture material (Monoplus 5-‐0, B Braun Australia Pty Ltd). A circumferential incision was made into the bladder around the diverticulum and the abnormal tissue was removed; the bladder was closed using a simple continuous followed by an inverting Cushing’s suture pattern using the same monofilament suture. Retrograde infusion of sterile saline into the urinary bladder using the technique previously described revealed no leakage from the incision site. The abdomen was then lavaged generously using prewarmed sterile 0.9% saline (Baxter Healthcare Pty Ltd) and the linea alba closed with 5-‐0 Monoplus in a simple continuous pattern followed by the skin in an intradermal suture pattern. Tissue glue (Vet Bond 3M Animal Care Products) was then carefully placed over the suture line to provide protection and strength. The abnormal urogenital tissue was then excised in a V shape using a scalpel and 0.04ml of epinephrine (Link Medical Products Warriewood NSW 2102) was then applied to facilitate vasoconstriction and subsequent haemostasis. The recovery was unremarkable and the guinea pig was eating shortly after surgery and appeared comfortable post operatively on meloxicam 0.2mg/kg and buprenorphine 0.02mg/kg subcutaneously.
The guinea pig was discharged 24 hours post operatively with a five day course of 0.5 mg/kg meloxicam PO q12hrs and 15mg/kg sulfamethoxazole and trimethoprim oral suspension PO q12hrs for 14 days. The guinea pig was rechecked by the referring veterinarian ten days later and was reported to be eating, drinking and urinating well. There was no sign of blood in the urine and she had gained 100grams. Two weeks later the guinea pig presented to the Avian Reptile and Exotic Pet Hospital for a follow up examination and urinalysis. Again the guinea pig had been well in herself, she had maintained her weight and no blood had been seen in her urine. In house urinalysis was normal and a free catch urine sample was obtained for culture and sensitivity. The culture revealed a slow growing mix of two unknown populations of bacteria. This was attributed to growth of bacteria that originated from the vagina or circumanal folds and is considered unlikely the result of a persistent urinary tract infection.
DISCUSSION
This case report details a persistent remnant urachus and vesicourachal diverticulum in a guinea pig. This guinea pig also presented with an abnormal urethral opening. To the authors’ knowledge there are no reports in the literature of this condition in a guinea pig.
In other species such as the horse, the urachus may fail to close, or reopen because of dilation of the urachus before birth caused by umbilical torsion, umbilical infection or lifting the foal by the abdomen. Clinical signs include urine scalding of the hindlimbs, dysuria, pollakiuria and apparent urinary incontinence. Affected horses cannot completely empty the bladder as a result of the bladder adhesions to the umbilicus. Based on the ultrasound findings and clinical history in this case, it appears that guinea pigs have a pathophysiology similar to that described for horses. In this case, the inability to empty the bladder appears to have lead to chronic cystitis and perineal scalding; this guinea pig also had an abnormal urethra, which would have added to the urinary retention and subsequent bacterial infection.
Other causes of urinary tract diseases in guinea pigs include cystitis, urolithiasis and chronic interstitial nephritis. Clinical signs of cystitis or lower urinary tract infections may present as an acute, ulcerative inflammatory process with haematuria that the owner notices as blood spots in the cage or in the vulva or prepuce (Johnson-‐Delaney 1998). Urolithiasis is a common problem in guinea pigs and was historically seen in older female guinea pigs (Hawkins and Bishop 2012) until a recent study found equal distribution of males and females over 2 years of age. Chronic interstitial nephritis is commonly found in guinea pigs more than 3 years of age and can lead to chronic renal failure.
Labial fusion also known as labial agglutination or synechia vulvae is an acquired condition caused by midline adherence of the vulvar labia minora (Plavec and Pavlin 2012). In humans this condition is reported to occur in up to 1.8% of female prepubertal patients. The most common cause is a predisposition to chronic irritation of the perivulvar skin due to poor hygiene, dirty nappies, senile vaginitis or local trauma among others. Most
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patients are asymptomatic and about 80% of cases resolve spontaneously within 1 year. If treatment is needed, topical use of oestrogen or corticosteroids are used while surgical correction is used for non-‐responsive medical cases and severe cases. Literature searches for labial fusion in animals revealed only 2 cases, both in cats. In 2010, Przywara et al., reported a case of labial fusion as a result of a cat fight wound; a prepubic urethrostomy and vaginoplasty were undertaken to correct the defect. Then in 2012, Plavec and Pavlin published a case report on the surgical correction of labial fusion with vaginoplasty in a 16month old neutered domestic short hair cat. The underlying cause of this abovementioned case was unknown and it was speculated the aetiology was similar to that of humans. Due to the rarity of the clinical presentation in domestic animals, a similar aetiology in this case can also only be hypothesised.
Treatment of remnant urachal tissue and bladder diverticula in animals is the same as humans and aims to resolve urinary disorders and restore normal bladder anatomy (Mesaric and Modic 2003; Iuchtman et al, 1993). Surgical removal of the urachal remnant and abnormal bladder tissue leads to curative surgical correction and resolution of chronic urinary tract infections. In this case, surgical correction of imperforate hymen was considered an important part of the treatment by allowing urine to exit freely from the urethra and not pool thereby reducing the chance of future infections.
Given the extensive clinical history of the guinea pig in this report, surgical correction was elected and removal of the remnant urachal stalk, bladder diverticulum and persistent vestibulovaginal membrane resulted in a cure for the dysuria and haematuria. Despite the follow up culture and sensitivity growing a mixed population of bacteria, the guinea pig remained clinical healthy with no apparent abnormalities ten months post operatively.
It follows then, that surgical correction of a persistent urachal remnant and vesicourachal diverticulum is a suitable and effective treatment in guinea pigs as it is in other species.
References
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