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==Signalment==

==Signalment==

Have only been confirmed in dogs although they may occur in cats. Predisposed breeds include:

Have only been confirmed in dogs although they may occur in cats. Typically older bitches (greater than 10 years) are affected (90% of cases) however male dogs are occasionally affected. Predisposed [[Canine Breeds - WikiNormals|dog breeds]] include the German shepherd dog, cocker spaniel, welsh spaniel and standard dachshund.

Image:Standard Dachshund (Short-haired).jpg|Daschunds

*Mainly older bitches (90%)

*Also in castrated male dogs

 

A highly malignant neoplasia that readily metastasizes to the medial iliac lymph nodes. Around 50% may lead to paraneoplastic hypercalcaemia due to parathyroid hormone-related peptide. The tumours can be between 1 and 10cm in size and 50% of them will metastasize.  

==Diagnosis==

==Diagnosis==

===History and Clinical Signs===

===History and Clinical Signs===

See [[Anal Sac Disease - General - WikiClinical|Anal Sac Disease - General]]

See [[Anal Sac Disease - General|Anal Sac Disease - General]]

Also:

Also:

*Obstipation due to enlarged internal iliac lymph nodes

'''Obstipation''' due to enlarged internal iliac lymph nodes and Perineal swelling. Additionally signs of '''hypercalcaemia''' including polydipsia, polyuria, anorexia and weight loss.

*Pernieal swelling

*Hypercalcaemia signs including polydipsia and polyuria.

===Rectal examination===

===Rectal examination===

Best carried out under general anaesthetic with manual compression of the caudal abdomen towards the rectum.

Tumours of the anal sac can be detected by digital rectal palpation of the anal sac and associated structures, this must be performed with care as frequently the tumours are small and unilateral. Best carried out under general anaesthetic with manual compression of the caudal abdomen towards the rectum.

===Biochemistry===

===Laboratory Tests===

To assess:

'''Serum Biochemistry''':

Hypercalcaemia is present in 50%-90% of dogs with anal sac adenocarcinoma. This is thought to occur due to the expression of a gene for  parathyroid hormone-related peptide by the tumour. Parathyroid hormone-related peptide has actions similar to parathyroid hormone, it acts to increase calcium levels in the blood. In severe cases of hypercalcaemia organ function can become compromised changing specific parameters on the biochemistry panel.

*Renal function

At least two views to check for thoracic metastases.

Patients may be dehydrated with a pre-renal azotaemia due but have a relatively low urine specific gravity.

===Abdominal imaging===

===Radiography===

Caudal lateral abdominal radiographs or abdominal ultrasound to assess the medial iliac lymph nodes for metastases. When enlarged the displace the rectum ventrally as they are found ventral to the lumbar sacral disc.

At least two views to check for thoracic metastases.  

===Needle biopsy===

====Abdominal imaging====

Guided by ultrasound to aspirate the effected lymph nodes.

Caudal lateral abdominal radiographs or abdominal ultrasound to assess the medial iliac lymph nodes for metastases. When enlarged they  displace the rectum ventrally.

 

 

Ultrasound guided needle biopsy and histopathology of the effected lymph nodes.

==Treatment==

==Treatment==

===Adjuvant radiotherapy===

===Adjuvant radiotherapy===

Can reduce the local recurrence and used if excision is incomplete. However it may lead to radiation-induced colitis.

Can reduce the local recurrence and used if excision is incomplete. Radiotherapy, however may lead to radiation-induced colitis.

===Palliative chemotherapy===

===Palliative chemotherapy===

===Treatment of Hypercalcaemia===

===Treatment of Hypercalcaemia===

High fluid rates of 0.9% saline to diurese calcium. Furosemide should be administered (2mg/kg intravenously) once the patient in normocalcaemic.

High fluid rates of 0.9% saline to diurese calcium. Furosemide should be administered once the patient in normocalcaemic.

==Prognosis==

==Prognosis==

Potential postoperative complications include infection, wound dehiscence, faecal incontinence and in 25% of cases, local recurrence. Hypercalcaemia reoccurs in 35-50% of cases due to metastases. Serum calcium levels should therefore be reguarly along with evidence of mass regrowth. Post-op survival ranges between 2 and 39 months with the average being 8 months

Potential postoperative complications include infection, wound dehiscence, faecal incontinence and in 25% of cases, local recurrence. Hypercalcaemia reoccurs in 35-50% of cases due to metastases. Serum calcium levels should therefore be regularly checked along with evidence of mass regrowth. Post-op survival ranges between 2 and 39 months with the average being 8 months.

 

==References==

==References==

Dobson, J.M. and Lascelles, B.D.X. (2003) '''BSAVA Manual of Canine and Feline Oncology (2nd Edition)''' ''BSAVA''

Dobson, J.M. and Lascelles, B.D.X. (2003) '''BSAVA Manual of Canine and Feline Oncology (2nd Edition)''' ''BSAVA''