Welcome to Justanswer! I am Dr. Altman and happy to assist you both today!
There are a handful of causes of blood from Max's penis which often originates in the bladder:
1.) A urinary tract infection, including possible prostate inflammation if he is not neutered
2.) Bladder stones that traumatize the bladder and cause bleeding
3.) A bladder tumor, most likely in a senior pet
4.) Trauma- hit by car, muscle trauma of some kind
Ideally until you are able to get to your veterinarian, please increase water intake. You can do this by supplementing the dry food with water and flavoring the water (maple syrup or no salt broth for example) as well. Increasing the water intake will help "flush" out the bladder and reduce the pain associated with the bleeding. Please also try to minimize licking which introduces oral bacteria to the area and increases irritation and risk of infection
Collecting a first morning sample in a tupperware container and refrigerating the sample if more than an hour old to have your vet evaluate the sample will help determine the cause of the blood within his prepuce or penis.
Your vet will start with an examination of the genitalia and run a urinalysis, potentially do a urine culture to look for bacteria, an X-ray to rule out a bladder stone, and bloodwork to ensure there is not a metabolic cause or kidney issues causing the symptoms
Diagnosing the issue will help determine how best to treat the blood from the penis which again is often related to the urinary tract to get your pet comfortable swiftly
Below is more information on this condition in dogs, called hematuria (blood in urine):
Please let me know if you have any additional questions I can assist with, I am online another 15 minutes tonight. If he is straining to urinate with only blood and no urine, only dripping urine or blood, gums are pale, unable to rest comfortably, or overly lethargic please consider a veterinary er tonight as he could potentially be obstructed which is a true emergency
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