The Japanese military did have an established medical corps with echelons of care (platoon level enlisted medic->Battalion Aid station with doctors->regimental hospital->Evacuation from theater).

There's two reasons you do not hear much about them:

1. The Japanese military in active combat against the Pacific suffered appalling losses, often fighting to the point of total destruction. Correspondingly outside of very rare diaries, or the few POWs, many battles are only known extensively through the Allied accounts, or the high-tier Japanese logs.

2. The capabilities of Japanese medical attention was very poor compared to their allied foes. The US medical establishment especially was at the end of a massive logistical effort, with an extensive system of out of theater evacuation for the severely wounded.

The Japanese generally had to make due with much less, and usually were fighting isolated from their supply lines due to successful sea interdiction.

For reference:

The Rising Sun by John Toland includes an extensive portion with an account by a Japanese civilian pressed into augmenting a military field hospital staff.

This article also proved to be interesting. While I can't vouch for the author, the sources look solid:

http://www.academia.edu/2898317/The_Paradox_of_the_Imperial_Japanese_Army_Medical_Department