• General surgery
• Colorectal surgery

• Familial Adenomatous Polyposis
• Inherited bowel cancer
• Customized therapy for cancer

• Wasantha Wijenayake, Devaka Fernando; Diabetes in Sri Lanka. Diabetes Reviewes International, Vol. 7, No. 3, July 1998.
• K I Deen, W Wijenayake, Z M Hassan: Inter-sphincteric Resection for Low Rectal Cancer, Bombay Hospital Journal, Vol.50, No.3, 2008.
  https://www.researchgate.net/profile/Wasantha_Wijenayake/publication/237514114_Inter-sphincteric_Resection_for_Low_Rectal_Cancer/links/556eac0e08aeab777226a95a/Inter-sphincteric-Resection-for-Low-Rectal-Cancer.pdf
• Wasantha Wijenayake, Mahendra Perera, Jayantha Balawardena, Raeed Deen, S Ruwan Wijesuriya, Sumudu K Kumarage, Kemal I Deen: Proximal and distal rectal cancers differ in curative resectability and local recurrence, World J Gastrointest Surg 2011 August 27; 3(8): 113-118
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192216/pdf/WJGS-3-113.pdf
• Colonoscopy-assisted laparoscopic resection of an obstructing 'giant' lipoma of the transverse colon B Asantha De Silva *RaeedDeen* Wasantha Wijenayake, ANZ Journal of Surgery 03/2015; DOI:10.1111/ans.13039
• Wijenayake, W., 2019. Diversion following rectal cancer surgery. Sri Lanka Journal of Surgery, 37(2), pp.9-11. DOI: http://doi.org/10.4038/sljs.v37i2.8624
• Colonoscopy-assisted laparoscopic resection of an obstructing 'giant' lipoma of the transverse colon BA De Silva, R Deen, WK Wijenayake ANZ journal of surgery 85 (10), 785-786
  https://onlinelibrary.wiley.com/doi/abs/10.1111/ans.13039
• Use of a rectus abdominis muscle cube to seal presacral venous haemorrhage MSB Tillakaratne, CS Ekanayake, W Wijenayake, KI Deen Sri Lanka Journal of Surgery 32 (4)
  http://doi.org/10.4038/sljs.v32i4.8093

Presentations

• K D W Wijenayake, M Silva, K Alagaratnam; Substance Abuse and Trauma Related Emergencies. The Annual Sessions of the College of Surgeons of Sri Lanka. 17^th to 21^st of August 2004, Colombo, Sri Lanka.
• K D W Wijenayake, M T P R Perera, M Fernando, M V C De Silva, K I Deen, D Fernando; The Distribution of Colorectal Cancer in Sri Lankan Patients Warrants Flexible Sigmoidoscopy as Minimum Assessment. The joint Scientific Sessions of The College of Surgeons of Sri Lanka and British Association of Surgical Oncology. 18^th to 20^th of August 2005, Colombo, Sri Lanka.
• Grand round presentation at St Marks Hospital 27^th July 2012; Colorectal Surgery; Sri Lankan Experience (Coconut Shell to Harmonic Scalpel)
• K D W Wijenayake, R Perera, S A Gunawardena, K S Perera; Renal Colic: Are We Over Investigating? The Annual Sessions of the College of Surgeons of Sri Lanka. 17^th to 21^st of August 2004, Colombo, Sri Lanka

• President of the Ostomy Association of Sri Lanka since 2017
• Past assistant secretory of college of surgeons of Sri Lanka
• Assistant Treasurer of College of Surgeons of Sri Lanka (Currently)
• Fellow of the College of Surgeons of Sri Lanka (FCSSL)
• Member of St Marks Association London, UK
• Member Royal College of Surgeons England
• Gastrointestinal and Digestive Endoscopy Society of Sri Lanka