An unexplained episode and more x-rays

Belka managed to give everyone quite a scare last night. The following is a chronological breakdown of events that cumulated in an emergency vet visit, x-rays, and one very disgruntled guinea pig.

1 AM: Spotted three small patches of urine with blood around/in the newly changed cage. An inspection of the occupants revealed the culprit to be Belka, who had a small amount of blood visible in the Y crevasse of her genital opening.

As observed ~ 1 AM

1:50 AM: Observed Belka peeing. The expelled urine was a bright red color with a tiny dark red splotch that wouldn't pass through the fleece bedding as liquids typically do. The texture was vaguely gritty with no accompanying mucus or pus. She showed no outwards sign of pain or discomfort, she did not squeak or appear uncomfortable while peeing and proceeded to eat cecals (her own poop) afterwards.

Picture taken immediately after urination

6 AM: Sat Belka in a sterile environment and syringe fed her over 30 cc of water in an effort to get her to produce urine for a sample. Of course, she refused to cooperate and insisted on holding it in while preparations were made to bring her in for an emergency vet visit.

7 AM: Belka finally peed during the drive to the vet. Confusingly enough, the urine was clear with not even a hint of pink - nevertheless a sample was taken and bottled.

@VET: Belka's weight recorded as 1260 grams, which is fairly normal for her if not even a little higher than usual. Our vet did not find anything wrong after a physical exam and palpation so he put her in line for an x-ray.
The urinalysis results came back normal, which eliminated the possibility of an UTI. Meanwhile, Belka wheeked and shrieked for the ASPCA almost every time she was held down for the x-ray scan. After taking a look, our vet said the x-rays themselves did not show anything amiss - he did not see stones or sludge in the bladder or along the ureters - and commented that she looked healthy and robust otherwise. He discussed a few possibilities (pyometra was ruled out as she had not excreted any accompanying pus) but ultimately felt it was fine to send her home.

Unfortunately, this wasn't the first time for Belka. The same thing occurred, but only once before in March with similarly inconclusive results. The tinted urine came and went within the same 6-9 hour time span. By the time Belka got to the vet the next morning, her urine was free of coloring and a urinalysis came up normal.

Guinea Lynx records relating to the urinary system provided several informative accounts regarding stones, UTIs and interstitial cystitis. However, none quite matched Belka's symptoms.

Afterwards, Belka returned to her cage and promptly took refuge in a hard-to-reach pigloo to sleep. She is currently bouncing around her cage as if nothing has happened. End result? We aren't sure. As long as the rare episodes don't become chronic or cause pain, and Belka remains active, energetic and hungry there doesn't seem to be much else to do but keep an eye on her.