Colonoscopy clinicians in Irvine, California

CMS lists 45 clinicians with a primary specialty of Gastroenterology, Internal Medicine, Family Practice, or General Practice who have billed Medicare for at least one colonoscopy and practice in Irvine, California (details below).

Colonoscopy volume

Clinician	Colonoscopies billed	Percentile rank
Roxanne Lim, MD	562	99%
Philip Chen, MD	474	99%
Fang Yu, MD	428	99%
David Kaufman, DO	395	98%
Kumaravel Perumalsamy, MD	251	94%
Shahrooz Bemanian, MD	224	91%
Paul Lee, MD	193	88%
Lance Uradomo, MD	189	87%
Victor Yu	163	83%
David Choi, DO	161	82%
You-Jen Chou, MD	150	80%
James Lee, MD	142	78%
Matthew Oman, MD	142	78%
Gustavo Machicado, MD	137	77%
Bret Namihas, MD	130	75%
Heba Ashraf, MD	128	74%
Haig Najarian, MD	123	72%
James Lin, MD	103	65%
Caroline Hwang, MD	60	44%
Poneh Rahimi, MD	58	43%
Herbert Lee, MD	56	42%
Javed Sadiq, MD	53	40%
Rashmi Kumar, MD	51	39%
Jim Amerian, MD	45	35%
Omeed Alipour, MD	41	32%
Ardalan Babaknia, MD	40	32%
Bashar Sharma, MD	40	32%
Jun Ichi Ohara, MD	27	23%
Seper Dezfoli, MD	21	20%
Brian Lee, MD	11	13%
Jacques Van Dam, MD	11	13%
Danh Dan, MD	1-10	13% or below
Shireena Desai, MD	1-10	13% or below
Robert Kung, MD	1-10	13% or below
Patrick Lee, MD	1-10	13% or below
Henry Niho, MD	1-10	13% or below
Jeffrey Niizawa, MD	1-10	13% or below
Jeffrey Rauch, MD	1-10	13% or below
Jenny Risman, MD	1-10	13% or below
Victoria Sheen, MD	1-10	13% or below
Doan Trang Tran, MD	1-10	13% or below
Khoi Tran, MD	1-10	13% or below
James Wang, MD	1-10	13% or below
Yuki Young, MD	1-10	13% or below
Selena Zhou, MD	1-10	13% or below

Sorted by the number of colonoscopies billed to Medicare, highest first, not by quality or skill. CMS suppresses counts between 1 and 10 to protect patient privacy and publishes the range instead.

Understanding CMS Data

CMS's "Colonoscopy" category combines specific billing codes for colonoscopy to calculate the number of times each clinician billed Medicare for a "Colonoscopy." These include screening colonoscopy, diagnostic colonoscopy, and colonoscopy with biopsy or polyp removal. CMS's list also includes flexible sigmoidoscopy and laparoscopic appendectomy, so a clinician's count may include those procedures. CMS counts one procedure per patient per day, so a colonoscopy that included both a biopsy and a polyp removal counts once. CMS reports only procedures that clinicians billed to Original Medicare and Medicare Advantage. Therefore, CMS's procedure volume data does not include procedures that clinicians may have performed on patients who have other health care coverage (e.g., commercial insurance, self-pay, or the VA). Billing variation and coding errors can also affect CMS's data. Therefore, the number of procedures that CMS reports for a clinician may be higher or lower than the actual number of colonoscopies a clinician performed during the reporting period. Lastly, only clinicians with a primary specialty of Gastroenterology, Internal Medicine, Family Practice, or General Practice (as reported to Medicare) are presented.

Source: Centers for Medicare & Medicaid Services (October 2, 2026 release).