The color of healthy animal urine is affected by urinary pigment and urine volume, and usually ranges from light yellow to amber. Urine can be affected by various substances and show abnormal colors, among which red urine is the most common and is often related to important diseases. Red urine is defined in this article in a broad sense, ranging from red, yellowish brown to dark brown.

The main causes of red urine are summarized in Table 1. The most important causes are red blood cells, hemoglobin and bilirubin, but various other substances are also included. When diagnosing, it is necessary to first understand the cause of red urine and then explore its cause.

Steps in diagnosis There are three steps in diagnosing red urine:

①Collection of initial data (linitial database)

②Identification of red urine

③Determination of the cause

1. Collection of initial data (Initial database)

Initial data include understanding the past medical history, understanding the current situation, observing urinary status, and conducting a comprehensive physical examination and urine examination.

(1) Understand past medical history

Ask the owner in detail whether the sick animals have past medical history of cystitis, urinary tract stones, trauma, chronic prostatitis, anemia, hemolytic disease, bleeding tendency, liver disease, etc.

(2) Grasp the current situation

Ask the owner in detail about the period, extent and course of the appearance of red urine in sick animals, the intensity of the red urine color during urination, recent treatment experience, food content and whether there are any signs of urinary disorders such as difficulty urinating and frequent urination.

(3) Observe urination status

If urinary disorder is suspected, the patient's urinary status needs to be actually observed. Difficulty urinating means that the urethra is narrowed or compressed, which may lead to suspicion of tumors, blood clots, urinary stones, etc. Frequent urination may lead to suspicion of prostatitis or cystitis.

(4) Comprehensive physical examination

In addition to the general physical examination, special palpation of the kidneys, bladder, prostate, urethra, and uterus is required, paying attention to their shape, size, hardness, and whether there is pain. In addition, check the penis, foreskin, vagina and other parts for bleeding, inflammation or tumors, etc. In addition, other surface mucosa should also be observed for bleeding tendencies, such as spotting, bleeding spots, black stools, etc.

(5) Urine test

A urine test must be taken before starting treatment. Urine collection can be done by natural urination, manual compression, catheter insertion, bladder puncture, etc. However, natural urination is easy to be contaminated. Among the three methods mentioned below, especially the manual compression method and the catheterization method, it is easy to cause iatrogenic hematuria. In addition, the catheterization method and bladder puncture method are also easy to cause bacterial secondary infection. Pros and cons. An appropriate combination of methods must be selected based on the actual situation.

If a 22-gauge needle is used to perform cystocentesis, it will basically not cause massive bleeding; if hematuria is suspected, natural urination is the first choice to avoid iatrogenic hematuria. However, natural urination will also mix blood, white blood cells, and bacteria from the genitals, which needs to be considered.

After collecting urine, perform the test as soon as possible. If the examination cannot be carried out immediately, the specimen should be stored in the refrigerator; the urine sample must be returned to body temperature before examination. Low-temperature urine samples are prone to crystallization, leading to misdiagnosis.

The urine sample should be divided into three parts for physical examination, chemical examination and urine sediment examination. Generally, it is easier to use test paper for general examination, but the urine sample must be centrifuged and the sediment should be taken for microscopic examination. The quantitative examination and evaluation method of urine sediment is to take a certain amount of urine (usually 5ml), centrifuge at 1,000 ~ 1,500rpm for 5 minutes. Normal urine has no more than 4-5 red blood cells in each field of view under high magnification (400 times).