Segment reporting The Companys business is comprised of its U.S. dialysis and related lab services business, various ancillary services and strategic initiatives, including its international operations, and its corporate administrative support. On June 19, 2019 , the Company completed the sale of its DMG division to Optum, a subsidiary of UnitedHealth Group Inc. As a result of this transaction, DMG's results of operations have been reported as discontinued operations for all periods presented. The Companys separate operating segments include its U.S. dialysis and related lab services business, each of its ancillary services and strategic initiatives, its kidney care operations in each foreign sovereign jurisdiction, its other health operations in each foreign sovereign jurisdiction, and its equity method investment in the APAC JV. The U.S. dialysis and related lab services business qualifies as a separately reportable segment, and all other ancillary services and strategic initiatives operating segments, including the international operating segments, have been combined and disclosed in the other segments category. The Companys operating segment financial information included in this report is prepared on the internal management reporting basis that the chief operating decision maker uses to allocate resources and assess the financial performance of the Company's operating segments. For internal management reporting, segment operations include direct segment operating expenses but generally exclude corporate administrative support costs, which consist primarily of indirect labor, benefits and long-term incentive-based compensation expenses of certain departments which provide support to all of the Companys various operating lines of business, except to the extent that such costs are charged to and borne by certain ancillary services and strategic initiatives via internal management fees. These corporate administrative support costs are reduced by internal management fees received from the Companys ancillary lines of business. The following is a summary of segment net revenues, segment operating margin (loss), and a reconciliation of segment operating margin to consolidated income before income taxes: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Segment revenues: U.S. dialysis and related lab services Patient service revenues: External sources $ 2,612,200 $ 2,612,734 $ 5,129,489 $ 5,101,899 Intersegment revenues 30,042 20,096 60,462 38,519 U.S. dialysis and related lab services patient service revenues 2,642,242 2,632,830 5,189,951 5,140,418 Provision for uncollectible accounts (10,249 ) (49,406 ) (15,712 ) (24,208 ) Net U.S. dialysis and related lab services patient service revenues 2,631,993 2,583,424 5,174,239 5,116,210 Other revenues (1) : External sources 5,209 4,919 9,893 10,033 Intersegment revenues 292  513  Total U.S. dialysis and related lab services revenues $ 2,637,494 $ 2,588,343 $ 5,184,645 $ 5,126,243 OtherAncillary services and strategic initiatives Patient service revenues, net $ 121,865 $ 105,669 $ 239,728 $ 207,925 Other external sources 113,680 213,037 222,419 440,748 Intersegment revenues 3,403 9,189 6,739 19,387 Total ancillary services and strategic initiatives revenues 238,948 327,895 468,886 668,060 Total net segment revenues 2,876,442 2,916,238 5,653,531 5,794,303 Elimination of intersegment revenues (33,737 ) (29,285 ) (67,714 ) (57,906 ) Consolidated revenues $ 2,842,705 $ 2,886,953 $ 5,585,817 $ 5,736,397 Segment operating margin: U.S. dialysis and related lab services $ 498,957 $ 449,443 $ 915,939 $ 882,822 OtherAncillary services and strategic initiatives (15,050 ) 2,815 (72,680 ) (4,175 ) Total segment operating margin 483,907 452,258 843,259 878,647 Reconciliation of segment operating margin to consolidated income from continuing operations before income taxes: Corporate administrative support (22,021 ) (14,066 ) (40,866 ) (29,769 ) Consolidated operating income 461,886 438,192 802,393 848,878 Debt expense (131,666 ) (119,692 ) (263,185 ) (233,208 ) Debt prepayment charges (12,160 )  (12,160 )  Other income, net 5,643 1,994 12,583 6,576 Consolidated income from continuing operations before income taxes $ 323,703 $ 320,494 $ 539,631 $ 622,246 (1) Includes management fee revenue from providing management and administrative services to dialysis ventures in which the Company owns a noncontrolling equity investment or which are wholly-owned by third parties. A summary of assets by reportable segment was as follows: June 30, 2019 December 31, 2018 Segment assets U.S. dialysis and related lab services (including equity investments of $101,161 and $95,290, respectively) $ 18,352,683 $ 12,333,641 OtherAncillary services and strategic initiatives (including equity investments of $124,516 and $129,321, respectively) 1,578,277 1,387,046 DMGHeld for sale (including equity investments of $0 and $4,833, respectively)  5,389,565 Consolidated assets $ 19,930,960 $ 19,110,252 Depreciation and amortization expense by reportable segment was as follows: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 U.S. dialysis and related lab services $ 144,621 $ 138,252 $ 285,401 $ 273,028 Other  Ancillary services and strategic initiatives 7,621 8,827 15,369 16,850 $ 152,242 $ 147,079 $ 300,770 $ 289,878 Expenditures for property and equipment by reportable segment were as follows: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 U.S. dialysis and related lab services $ 149,264 $ 197,051 $ 319,812 $ 388,458 OtherAncillary services and strategic initiatives 7,062 22,184 15,640 32,172 DMGHeld for sale 18,714 22,299 38,466 53,347 $ 175,040 $ 241,534 $ 373,918 $ 473,977