Malignant Obstructions

Tracheal Cancer

Tracheal stenting may be an option for obstructions of the trachea secondary to cancer. For cases of tracheal cancer, the purpose of the stent is to palliate your pet’s clinical signs (difficulty breathing) and to make him or her more comfortable by allowing easier passage of oxygen to the lungs.

Urethra / Bladder / Prostate Cancer

The urethra is the tube that carries urine from the bladder and expels it outside of the body. Tumors are commonly found in the bladder, urethra and prostate (males) in locations that can cause blockage of the urethra with a subsequent inability to expel urine. Several treatment options including oral medications, chemotherapy, radiation therapy and surgery have been utilized to treat these tumors. These treatments may be insufficient to treat the life-threatening complications associated with a complete blockage of the urethra.

In certain cases, the placement of a urethral stent may be necessary to allow for relief of the urethral obstruction. If your pet suffers from cancer of the bladder, urethra or prostate, please consult with a member of the oncology service to determine if a urethral stent may be an appropriate treatment option.

Chemotherapy may be included in the treatment of tumors causing malignant urethral obstruction. (Mutsaers 2003, Freitag 2007) Additionally, radiation therapy is often utilized to treat prostatic neoplasia in dogs and may be considered for urethral and bladder tumors as well.

While surgical debulking/resection, chemotherapy and radiotherapy may be potential treatment options for initial treatment of non-obstructive urethral neoplasia, these are not good options for immediate relief of complete urethral obstruction secondary to neoplasia. Palliation of urethral obstruction by the placement of a urethral stent has been extensively described in human clinical medicine (Sertcelik 2000, DeVocht 2003) and experience is increasing in veterinary clinical medicine. (Weisse 2006)

Ureteral Obstruction Secondary to Cancer

Dogs and cats have two ureters. The ureter is the tube connecting the kidney to the bladder and has the responsibility of carrying urine to the bladder after it is formed in the kidney. Malignant (cancerous) obstruction of the ureter is generally secondary to cancer that originates in the bladder or urethra and extends over the ureteral opening into the bladder.  Obstruction can prevent urine from traveling to the bladder which may be a life-threatening condition.

Generally, for malignant ureteral obstructions, stenting involves the placement of a tube within the ureter that extends from the kidney to the bladder to allow for the passage of urine. This is performed through the skin without an incision which allows for minimally invasive placement of a stent.

Vascular Obstruction Secondary to Cancer

Blood vessels can become blocked by tumors resulting in an inability of blood to flow through those vessels. Signs may develop secondary to poor blood flow or a decreased ability for blood to return to the heart. Stents can be placed into the blood vessel to open the blood vessel and allow blood to flow more effectively.

Colorectal Cancer

Colon cancer in veterinary patients is most often treated by surgical removal. While surgery is associated with some morbidity, successful outcomes can be obtained. In very select cases of colorectal cancer, the tumor is too large to be removed or is located in an area preventing complete removal. Medical management to ease the expulsion of feces may still be tried in these cases but is often unsuccessful. 

In cases where a patient is not successfully treated with medical and/or surgical management, the placement of a colonic stent may be considered. A metal or metal-alloy stent that generates outward force can provide an opening in the colon to allow for the passage of feces. In most cases, medical management post-stent placement is still required, however, the goal of the procedure is to significantly improve the pet’s quality of life.

Colorectal stenting has been extensively described in human medicine for the treatment of both benign and malignant colorectal tumors. Colorectal stents in humans have 2 primary indications: as a “bridge to surgery” which allows for patient stabilization prior to undergoing an elective procedure or to palliate clinical signs. (Davies 2004, Watt 2007, Kim 2008) In the “bridge to surgery” group, stent placement prior to undergoing an elective procedure has been shown to improve outcome (less complications, less unnecessary operations). (Santos-Martinez 2002) As opposed to major surgical resection or colostomy stoma formation, some patients elect to have a stent placed to palliate clinical signs. (Athreya 2006)

Colonic stenting has been reported in 2 cats and 1 dog. (Hume 2006, Culp 2011) In one cat, clinical signs were limited to mechanical obstruction of the colon, despite the presence of suspected pulmonary metastatic disease at the initial evaluation. The clinical signs improved after stent placement in this cat, and tenesmus was rarely observed; fecal incontinence was not reported. Despite the presence of multiorgan metastasis at the time of euthanasia (the colonic tumor was noted to be an adenocarcinoma), the cat survived for 274 days post-stent placement. (Hume 2006)  In the single canine case report, successful stent placement was noted and clinical signs improved for just over 200 days. (Culp 2011)