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    

1. Baxter   GM,   Darien   BJ   and   Wallace   CE   (1987).  Persistent   urachal   remnant   causing   intestinal  strangulation  in  a  cow.  Journal  of  the  American  Veterinary  Medical  Association  191,  555-­‐558.    

2. Hawkins  MG  and  Bishop  CR  (2012).  Chapter  23:  Disease   Problems   of   Guinea   Pigs.   In  Quesenberry  KE  and  Carpenter  JW  (eds),  Rabbit  Rodents   and   Ferrets,   Clinical   Medicine   and  Surgery.  Elsevier  Saunders,  St  Louis,  Missouri.      

3. Johnson-­‐Delaney   CA   (1998).   Disease   of   the  Urinary   System   of   Commonly   Kept   Rodents:  Diagnosis   and   Treatment.   Seminars   in   Avian  and  Exotic  Pet  Medicine  7(2),  81-­‐88.  

4. Laverty   PH   and   Salisbury   SK   (2002).   Surgical  management   of   true   patent   urachus   in   a   cat.  Journal  of  Small  Animal  Practice  43,  227-­‐229.    

5. Lojszczyk-­‐Szczepaniak   A,   Smiech   A   and  Wojnowski   T   (2010).   Congenital   urachal  diverticulum   in   dogs:   a   case   report.  Medycyna  Weterynaryjna  66  (6),  421-­‐424.    

6. Iuchtman   M,   Rahav   S,   Zer   M,   Mogilner   J   and  Siplovich   L   (1993).   Management   of   urachal  anomalies   in   children   and   adults.   Urology   42  (4),  426-­‐430.    

7. Mesaric  M  and  Modiac  T,  (2003).  Strangulation  of  the  small   intestines   in  a  cow  by  a  persistent  urachal   remnant.   Veterinary   Record   153   (22),  688-­‐689.    

8. Plavec   T   and   Palvin   D,   (2012).   Surgical  correction   of   labial   fusion  with   vaginoplasty   in  cat.   Journal   of   Feline   Medicine   and   Surgery  15(6),  520-­‐523.    

9. Przywara   J,   Byron   J,   Bennett   RA,   Ham   K,  Greenfield   CL,   and   Steele   K,   (2010).   Prepubic  urethrostomy  and  vaginoplasty  in  a  female  cat.  Journal   of   the   American   Animal   Hospital  Association  46,  439-­‐443.    

10. Hargaden  M   and   Singer   L   (2012).   Chapter   20:  Anatomy   Physiology   and   Behavior.   In   Suckow,  MA,   Stevens   KA   and   Wilson   RP,   (eds).   The  laboratory   rabbit,   guinea   pig,   hamster,   and  other  rodents.  1st  ed,  Amsterdam,  Boston.  

11. Turner   PV,   Harkenss   JE,   Wheler   CL   and  VandeWoude   S   (2013),   Chapter   2:   Biology   and  Husbandry,   The   Guinea   Pig.   In   Harkness   and  Wagner's  Biology  and  Medicine  of  Rabbits  and  Rodents,  5th  edn,  Wiley,  Hoboken.