Inflammatory diseases of the bladder cause the urgent urge to urinate. Dysuria means frequent urination of small volumes of urine, often with straining.
Dysuria is the classic sign of cystitis.
There is not enough information given to decide whether it is an acute or chronic disease. You would need additional diagnostic tests, such as abdominal radiographs or renal ultrasound, to determine renal size for example, to determine whether this dog's renal insufficiency is acute or chronic. C Pyometra is not likely here since the dog has no vaginal discharge, no leukocytosis, and, if the history is accurate, she should be in anestrus, not metestrus. Nevertheless she is intact and pyometra is treated differently than renal failure. The normal serum potassium suggests she is not oliguric.